fix: added login_hint to the idp intent (#11552)

# Which Problems Are Solved

In login V2, when the user started the login flow of an external IDP,
there was no login_hint passed to the external provider. This required
the user to enter their username again. Whilst they already entered it
in Zitadel. By adding the `login_hint` parameter, the username should
already be filled in on the external idp.

# How the Problems Are Solved

Pass the `login_hint` parameter to the external idp.

# Additional Changes

Also added the `login_hint` to the event-store for audit trailing.

# Additional Context


- Closes #11392

---------

Co-authored-by: Copilot <[email protected]>

internal/command/session_test.go

@@ -993,6 +993,7 @@ func TestCommands_updateSession(t *testing.T) {
 								nil,
 								nil,
 								"idpID",
+								"",
 								nil,
 							),
 						),