[vscode-shared] Refactor string marking logic into `runWorkspaceCommandAsync`

[TheLarkInn]

runWorkspaceCommandAsync used in two places:

rushstack/vscode-extensions/debug-certificate-manager-vscode-extension/src/extension.ts

Lines 210 to 226 in 98334a9

	const markerPrefix: string = '<<<HOMEDIR_START>>>';
	const markerSuffix: string = '<<<HOMEDIR_END>>>';
	const output: string = await runWorkspaceCommandAsync({
	terminalOptions: { name: 'debug-certificate-manager', hideFromUser: true },
	// Wrapping the desired node output in markers to trim uninteresting shell output.
	commandLine: `node -p "'${markerPrefix}' + require('os').homedir() + '${markerSuffix}'"`,
	terminal
	});
	terminal.writeLine(`Running command to resolve home directory: ${output}`);
	const startIndex: number = output.lastIndexOf(markerPrefix);
	const endIndex: number = output.lastIndexOf(markerSuffix);
	if (startIndex !== -1 && endIndex !== -1 && endIndex > startIndex) {
	homeDir = output.substring(startIndex + markerPrefix.length, endIndex).trim();
	} else {
	throw new Error('Failed to parse home directory from command output');
	}

and

rushstack/vscode-extensions/playwright-local-browser-server-vscode-extension/src/extension.ts

Lines 48 to 62 in 98334a9

	const markerPrefix: string = '<<<TEMPDIR_START>>>';
	const markerSuffix: string = '<<<TEMPDIR_END>>>';
	const output: string = await runWorkspaceCommandAsync({
	terminalOptions: { name: 'playwright-local-browser-server', hideFromUser: true },
	commandLine: `node -p "'${markerPrefix}' + require('node:os').tmpdir() + '${markerSuffix}'"`,
	terminal
	});
	const startIndex: number = output.indexOf(markerPrefix);
	const endIndex: number = output.indexOf(markerSuffix);
	if (startIndex !== -1 && endIndex !== -1 && endIndex > startIndex) {
	tempDir = output.substring(startIndex + markerPrefix.length, endIndex).trim();
	} else {
	throw new Error('Failed to parse temp directory from command output');
	}

with duplicate string marker logic wrapped around the usage of these functions.

We should abstract this as a new option in runWorkspaceCommandAsync so we don't have this extra logic.