feat(oauth/oidc): move token exchange from beta to GA (#11475)

# Which Problems Are Solved

This PR marks the OAuth2 Token Exchange as general available (GA).

# How the Problems Are Solved

- API:
- deprecated the feature toggle (to prevent breaking changes) in v2beta
and v2 API
- removed all related event logic and updated the projection interation
  - removed the toggle usage for token exchange
  - removed related translations
- Management Console:
  - removed the feature toggle and its translations
- Docs:
  - removed all beta labels and feature toggle notes

# Additional Changes

- removed unused `Errors.WebKey.FeatureDisabled` translations

# Additional Context

- closes #11114

---------

Co-authored-by: Marco A. <[email protected]>

internal/command/instance_features.go

@@ -15,7 +15,6 @@ import (
 type InstanceFeatures struct {
 	LoginDefaultOrg                *bool
 	UserSchema                     *bool
-	TokenExchange                  *bool
 	ImprovedPerformance            []feature.ImprovedPerformanceType
 	DebugOIDCParentError           *bool
 	OIDCSingleV1SessionTermination *bool
@@ -29,7 +28,6 @@ type InstanceFeatures struct {
 func (m *InstanceFeatures) isEmpty() bool {
 	return m == nil || (m.LoginDefaultOrg == nil &&
 		m.UserSchema == nil &&
-		m.TokenExchange == nil &&
 		// nil check to allow unset improvements
 		m.ImprovedPerformance == nil &&
 		m.DebugOIDCParentError == nil &&