Update Yarn and Better Document Dependencies

[elijah-potter]

#688 informed me that Harper has been using an old (deprecated) version of Yarn. This PR updates the referenced Yarn version in our package.json files and modifies our tooling to work with it.

I've also added a short blurb about certain integration test dependencies on certain Linux platforms.

@shanecranor, does this look good to you?

[shanecranor]

LGTM, maybe add some stuff to the .gitignore https://yarnpkg.com/getting-started/qa#which-files-should-be-gitignored

oops, I sent that before just setup finished, I'm getting some errors that I wasn't before

error: Cannot find module '/home/shane/tmp_stuff/harper/packages/vscode-plugin/build/tests/runTests.js'
    at Function._resolveFilename (node:internal/modules/cjs/loader:1405:15)
    at defaultResolveImpl (node:internal/modules/cjs/loader:1061:19)
    at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1066:22)
    at Function._load (node:internal/modules/cjs/loader:1215:37)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:235:24)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:151:5)
    at node:internal/main/run_main_module:33:47 {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}
Node.js v23.8.0
error: Recipe `test-vscode` failed with exit code 1

[mcecode]

oops, I sent that before just setup finished, I'm getting some errors that I wasn't before

error: Cannot find module '/home/shane/tmp_stuff/harper/packages/vscode-plugin/build/tests/runTests.js'
    at Function._resolveFilename (node:internal/modules/cjs/loader:1405:15)
    at defaultResolveImpl (node:internal/modules/cjs/loader:1061:19)
    at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1066:22)
    at Function._load (node:internal/modules/cjs/loader:1215:37)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:235:24)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:151:5)
    at node:internal/main/run_main_module:33:47 {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}
Node.js v23.8.0
error: Recipe `test-vscode` failed with exit code 1

This is because Yarn >=2.x no longer automatically runs pre and post scripts outside of set lifecycle scripts, so the tests aren't being built before Yarn tries to run them.

We can remedy this by merging the pretest command with the test command in packages/vscode-plugin/package.json:

	"scripts": {
		"watch:esbuild": "node esbuild.cjs --watch",
		"watch:tsc": "tsc --noEmit --watch",
-		"pretest": "yarn lint && tsc && node esbuild.cjs",
+		"test": "yarn lint && tsc && node esbuild.cjs && node build/tests/runTests.js",
		"vscode:prepublish": "yarn lint && tsc --noEmit && node esbuild.cjs --production",
		"package": "vsce package",
		"lint": "eslint src --ext ts"
	},

I'd do it myself but I don't think I have access to this branch to add changes so leaving the fix here.

This should also fix the failing precommit workflow.

[mcecode]

I just realized because of the failing test that a blocker in doing this Yarn migration is @vscode/vsce, which is what's used to package and publish VS Code extensions. It only officially supports Yarn 1.x. Though, there is a workaround that might work for us since we also use esbuild to bundle our extension.