Enable pwsh-script-integration provider by default and remove parts of it

[Tyriar]

• Blocked on Move terminal bits out of simpleCompletionItem #239813

Since we now have good general completions coming from terminal-suggest and will soon get deeper fig-powered ones, I've ripped out a bunch of stuff from the pwsh-script-integration provider. However I also enabled it by default and it now exclusively provides non-file/folder argument completions as options.

These are all terminal-suggest completions:

These contain both, with pwsh props at the top and files from terminal-suggest's fallback at the bottom:

This should give the best of both worlds, at least until we iterate more on the pwsh completions inside terminal-suggest.

Note that I also removed the code and git tab completion providers and the terminal.integrated.suggest.builtinCompletions setting since fig completions will replace it in a shell-agnostic way soon.

cc @TylerLeonhardt

[meganrogge]

👍🏼

The merge-base changed after approval.