Commit Message: envoy_log: allows Envoy version embedding
Additional Description:
We are running multiple Envoy versions on a same VM instance sometimes, so the Envoy's application logs are sometimes interleaved with different Envoy versions, which made it a little bit harder for us to debug later.

This commit adds a new 'E' specifier in the application log to bundle the envoy version in the log line.

Risk Level: low (new code path)
Testing: done
Docs Changes: done
Release Notes: done
Platform Specific Features: n/a

Request variables

Key	Value
ref	33582c2
sha	975a8d5
pr	44337
base-sha	d4fd8e3
actor	@mathetake
message	envoy_log: allows Envoy version embedding...
started	1775766473.681292
target-branch	main
trusted	false

Container image/s (as used in this CI run)

Envoy version (as used in this CI run)