Update SPFx documentation and tutorials: Gulp-based toolchain → Heft (SPFx v1.22 GA)

[Ashlesha-MSFT]

This is a tracker for content updates related to the SPFx v1.22 GA release, which includes the deprecation of the legacy Gulp-based toolchain in favor of the new Heft-based toolchain.

Summary:
SPFx v1.22 GA officially deprecates the Gulp-based toolchain. All SPFx learning tutorials and documentation that reference Gulp tasks (gulp serve, gulp bundle, etc.) should be updated to use the Heft-based toolchain.

This issue tracks the migration of affected documentation in alignment with the Documentation and Tutorial

Affected Content (examples):
Tutorials:

1. https://learn.microsoft.com/en-us/sharepoint/dev/spfx/web-parts/get-started/build-a-hello-world-web-part
2. https://learn.microsoft.com/en-us/sharepoint/dev/spfx/web-parts/get-started/connect-to-sharepoint