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/system_features_test.go

@@ -289,7 +289,6 @@ func TestSystemFeatures_isEmpty(t *testing.T) {
 		{name: "empty features", sysFeatures: &SystemFeatures{}, want: true},
 		{name: "LoginDefaultOrg set", sysFeatures: &SystemFeatures{LoginDefaultOrg: gu.Ptr(true)}, want: false},
 		{name: "UserSchema set", sysFeatures: &SystemFeatures{UserSchema: gu.Ptr(true)}, want: false},
-		{name: "TokenExchange set", sysFeatures: &SystemFeatures{TokenExchange: gu.Ptr(true)}, want: false},
 		{name: "ImprovedPerformance set", sysFeatures: &SystemFeatures{ImprovedPerformance: []feature.ImprovedPerformanceType{}}, want: false},
 		{name: "OIDCSingleV1SessionTermination set", sysFeatures: &SystemFeatures{OIDCSingleV1SessionTermination: gu.Ptr(true)}, want: false},
 		{name: "EnableBackChannelLogout set", sysFeatures: &SystemFeatures{EnableBackChannelLogout: gu.Ptr(true)}, want: false},