Test: New RelativePattern support in extension APIs

[bpasero]

Refs: #34157

• Windows - @mjbvz
• Linux - @jrieken
• macOS - @kieferrm

Complexity: 3

We have 3 places where we ask for a file glob pattern:

• workspace.createFileSystemWatcher
• workspace.findFiles(include, exclude))
• DocumentFilter#pattern

To make it easier to scope a pattern to a WorkspaceFolder, we introduced RelativePattern which allows to specify a base and a pattern to match against. Only file paths that are within that base file path are considered a match for the pattern.

Verify:

• the documentation around the 3 APIs mentioned above makes sense and is helpful
• you can use the 3 APIs from your extension and they work with either string or RelativePattern as documented.

FYI - to test against the latest API do the following:

open your extensions package.json file
change the engine.vscode property to *
run npm run postinstall (assuming you have the vscode module as dev-dependency)
undo the engine-version change from step 2

[bpasero]

@mjbvz fyi due to my change in #35103 the order of ctor arguments has changed. This shouldn't be a problem if you test on todays insider where the change is in.