detect files that don't need to be linted in no-internal

[MichaelBelousov]

In workspaces or general linting of large amounts of code which do not always use @itwin/@bentley packages, it is possible to avoid expensively checking every identifier by first determining whether the file is in a package with dependencies that we want to check for @internal APIs at all. Hide it behind an "experimental" option

In a local project this provided me a 33% speed up in a particular build pipeline

• fix utility that adds skip/only utility to tests
• remove workspace-tools dep and just manually hunt for the package.json since I need the same thing but working without workspaces
• fix issue where link fixtures script fails on second run

[MichaelBelousov]

found some issues, redrafting to fix