feat(oidc): provide actor information in userinfo actions (#12566)

# Which Problems Are Solved

Expose impersonating actor to `preAccessToken` and `preUserinfo`
actions.

# How the Problems Are Solved

Provide the `actor` information already present in the OIDC session
model of JWT token to the relevant actions. Both goja-based actions "v1"
and webhook based execution targets carry the actor information now.
Actor remains null in case of non-impersonated tokens. Actor may contain
nested actors to display a delegation chain of impersonators.

# Additional Changes

- dba6261c8ed0dfd00ffde6193910b1405b17432f: refactor `userinfoFlows` to
reduce complexity, add test coverage and solve a couple of potential
bugs.
- `getClientId` in actions was previously undocumented. Added to
documentation.
- A skill that reproduces manual testing using webhook.site or a local
sink.

# Additional Context

- Closes https://github.com/zitadel/zitadel/issues/12097

---------

Co-authored-by: Claude Sonnet 5 <[email protected]>
Co-authored-by: Copilot Autofix powered by AI <[email protected]>
Co-authored-by: Wim Van Laer <[email protected]>

.gitignore

@@ -33,6 +33,7 @@ google-credentials
 key.json
 .keys/*
 load-test/.keys
+*.pat
 
 # dumps
 .backups
@@ -82,8 +83,6 @@ build/local/*.env
 /zitadel
 node_modules/
 .kreya
-login-client.pat
-admin.pat
 .env.*local
 
 go.work