We now create npm packages to cover all the public api assertions in tools/public_api_guard.
We no longer depend on ts-api-guardian from npm - it is now stale since the repository was archived.
There is no longer a gulp task to enforce or accept the public API, this is in CircleCI as part of running all bazel test targets.
PR Close#22639
* Remove now unnecessary portions of build.
* Add a compilePackageES5 method to build ES5 from sources
* Rework all package.json and rollup config files to new format
* Remove "extends" from tsconfig-build.json files and fixup compilation roots
PR Close#18541
