KEP-4193: bound service account token improvements (#4141)

* add requester info in JWTs kep

* updates after sig-auth call

* update KEP to only include embedding Node info + JTIs

* fill out additional PRR sections

* Apply suggestions from code review

Co-authored-by: Mo Khan <[email protected]>

* Address review feedback

* add prod-readiness entry for kep 4193

* add clarifications around metrics and feature enablement

* Details on safe rollback planning

* rename KEP directory

* remove verifying pod tokens embedded node info and update feature flags

* update-toc

* final updates

---------

Co-authored-by: Mo Khan <[email protected]>

Author: munnerz

keps/prod-readiness/sig-auth/4193.yaml

@@ -0,0 +1,3 @@
+kep-number: 4193
+alpha:
+  approver: "deads2k"