fix unit test set-up and CI workflow (#3154)

* Fix unit test set-up

* run tests on CI

* update failing tests

* Update node

Update the coverage job node version

src/test/requires.ts

@@ -0,0 +1,17 @@
+const Module = require("module")
+const originalRequire = Module.prototype.require
+
+/**
+ * VSCode is not available during unit tests
+ * @see {@link file://./vscode-mock.ts}
+ */
+Module.prototype.require = function (path: string) {
+	if (path === "vscode") {
+		return require("./vscode-mock")
+	}
+
+	return originalRequire.call(this, path)
+}
+
+// Required to have access to String.prototype.toPosix
+import "../utils/path"

src/test/vscode-mock.ts

@@ -0,0 +1 @@
+export {}