Update SPFx use of legacy gulp-toolchain for Heft in v1.22 GA

[andrewconnell]

Important

This is a tracker for content updates related to the SPFx v1.22 GA release that includes the deprecation of the legacy gulp-based toolchain in favor of the new Heft-based toolchain. The toolchain shift impacts lots of docs across this repo.

🚧🚧 This is an ongoing project... use this to monitor progress 🚧🚧

This is related to #10515, which addressed high-level changes and guidance. This issue focuses on updating the how-to articles, tutorials, and pages that use the legacy gulp-toolchain.

Some pages can be easily updated, others will require more time to modernize the topic of the article.

---

catalog docs to update

• add md include explanation, change & plans for future update c5a0754

• find all instances of e9be876

  gulp build
  gulp bundle
  gulp package-solution
  gulp serve

• [ ] catalog simple updates & fix

decided to update does as sseperate PRs.