tsweb: switch to fastuuid for request ID generation

Request ID generation appears prominently in some services cumulative
allocation rate, and while this does not eradicate this issue (the API
still makes UUID objects), it does improve the overhead of this API and
reduce the amount of garbage that it produces.

Updates tailscale/corp#18266
Updates tailscale/corp#19054

Signed-off-by: James Tucker <james@tailscale.com>

cmd/derper/depaware.txt

@@ -17,7 +17,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
    L    github.com/google/nftables/expr                              from github.com/google/nftables+
    L    github.com/google/nftables/internal/parseexprfunc            from github.com/google/nftables+
    L    github.com/google/nftables/xt                                from github.com/google/nftables/expr+
-        github.com/google/uuid                                       from tailscale.com/tsweb
+        github.com/google/uuid                                       from tailscale.com/util/fastuuid
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
    L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces+
@@ -143,6 +143,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/util/ctxkey                                    from tailscale.com/tsweb+
    L 💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
         tailscale.com/util/dnsname                                   from tailscale.com/hostinfo+
+        tailscale.com/util/fastuuid                                  from tailscale.com/tsweb
         tailscale.com/util/httpm                                     from tailscale.com/client/tailscale
         tailscale.com/util/lineread                                  from tailscale.com/hostinfo+
    L    tailscale.com/util/linuxfw                                   from tailscale.com/net/netns
@@ -250,6 +251,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         math/big                                                     from crypto/dsa+
         math/bits                                                    from compress/flate+
         math/rand                                                    from github.com/mdlayher/netlink+
+        math/rand/v2                                                 from tailscale.com/util/fastuuid
         mime                                                         from github.com/prometheus/common/expfmt+
         mime/multipart                                               from net/http
         mime/quotedprintable                                         from mime/multipart

cmd/stund/depaware.txt

@@ -2,7 +2,7 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
 
         github.com/beorn7/perks/quantile                             from github.com/prometheus/client_golang/prometheus
      💣 github.com/cespare/xxhash/v2                                 from github.com/prometheus/client_golang/prometheus
-        github.com/google/uuid                                       from tailscale.com/tsweb
+        github.com/google/uuid                                       from tailscale.com/util/fastuuid
      💣 github.com/prometheus/client_golang/prometheus               from tailscale.com/tsweb/promvarz
         github.com/prometheus/client_golang/prometheus/internal      from github.com/prometheus/client_golang/prometheus
         github.com/prometheus/client_model/go                        from github.com/prometheus/client_golang/prometheus+
@@ -65,6 +65,7 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         tailscale.com/util/ctxkey                                    from tailscale.com/tsweb+
    L 💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
         tailscale.com/util/dnsname                                   from tailscale.com/tailcfg
+        tailscale.com/util/fastuuid                                  from tailscale.com/tsweb
         tailscale.com/util/lineread                                  from tailscale.com/version/distro
         tailscale.com/util/nocasemaps                                from tailscale.com/types/ipproto
         tailscale.com/util/slicesx                                   from tailscale.com/tailcfg
@@ -151,6 +152,7 @@ tailscale.com/cmd/stund dependencies: (generated by github.com/tailscale/depawar
         math/big                                                     from crypto/dsa+
         math/bits                                                    from compress/flate+
         math/rand                                                    from math/big+
+        math/rand/v2                                                 from tailscale.com/util/fastuuid
         mime                                                         from github.com/prometheus/common/expfmt+
         mime/multipart                                               from net/http
         mime/quotedprintable                                         from mime/multipart

tsweb/request_id.go

@@ -7,8 +7,8 @@ import (
 	"context"
 	"net/http"
 
-	"github.com/google/uuid"
 	"tailscale.com/util/ctxkey"
+	"tailscale.com/util/fastuuid"
 )
 
 // RequestID is an opaque identifier for a HTTP request, used to correlate
@@ -44,7 +44,7 @@ func GenerateRequestID() RequestID {
 	// REQ-1 indicates the version of the RequestID pattern. It is
 	// currently arbitrary but allows for forward compatible
 	// transitions if needed.
-	return RequestID("REQ-1" + uuid.NewString())
+	return RequestID("REQ-1" + fastuuid.NewUUID().String())
 }
 
 // SetRequestID is an HTTP middleware that injects a RequestID in the