Backport/2.5/39063 (#39093)

* Fix ios and iosxr terminal prompt regex (#39063)

Fixes #38732

Make matching leading newline for cli prompt
optional as there are cases when returned repsonse
for ios/iosx remote host doesn't have newline before
cli prompt.
(cherry picked from commit eebfa66c2b)

* Adding changelog for ios and iosxr terminal prompt fix

changelogs/fragments/ios_iosxr_terminal_prompt.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+- ios_iosxr_terminal - fixed issue with ios and iosxr terminal prompt regex