The Language Service integration tests should reinstall the Angular
distribution every time it is built. Adds a `yarn build-dist`
convinience script so building the distribution doesn't have to
happen on the repo root. This new script also refreshes the installed
modules. Building is expesnive, so it is not bundled with testing
scripts.
PR Close#32515
The documentation for the langauge service plugin integration test
appears to be stale. Remove section about new versions of TypeScript,
which appear not to be tested, and update the information about
generating and updating goldens to reflect the new way of doing so.
Add information about install deps in the repo root, this directory, and
building Angular before testing.
Also remove trailing whitespace on one line.
PR Close#32269