Angular sample updates for MSAL Angular v4 and Angular 19 support

[jo-arroyo]

This PR:

• Updates MSAL Angular docs with MSAL Angular v4 information and Angular 19 support
• Updates the angular18-standalone-sample to use Angular 19 and renames it angular-standalone-sample. This sample is moved to msal-angular-samples folder.
• Moves the following samples to the msal-angular-samples folder and ensure they work with MSAL Angular v4:
  • angular-b2c-sample
  • angular16-sample (renamed to angular-modules-sample)
• Removes the following v3 samples from the msal-angular-samples folder: (they continue to live on in the v3-lts branch)
  • angular-standalone-sample (basic sample that used Angular 16)
  • angular-15-sample
  • angular-17-standalone-sample
• Updates pipeline with renamed samples
• Updates roadmap with removal of Angular 19 support

Copilot reviewed 219 out of 230 changed files in this pull request and generated no comments.

Files not reviewed (11)

• samples/msal-angular-samples/angular-b2c-sample/angular.json: Language not supported
• samples/msal-angular-samples/angular-b2c-sample/package.json: Language not supported
• samples/msal-angular-samples/angular-b2c-sample/jest.config.js: Evaluated as low risk
• samples/msal-angular-samples/angular-b2c-sample/README.md: Evaluated as low risk
• .pipelines/3p-e2e.yml: Evaluated as low risk
• lib/msal-angular/docs/configuration.md: Evaluated as low risk
• roadmap.md: Evaluated as low risk
• lib/msal-angular/docs/angular-universal.md: Evaluated as low risk
• lib/msal-angular/docs/redirects.md: Evaluated as low risk
• lib/msal-angular/docs/events.md: Evaluated as low risk
• lib/msal-angular/FAQ.md: Evaluated as low risk