feat: add experimental bun package manager support

[jasongitmail]

Based on the existing NPM and PNPM versions.

I added a test file, based on the test/npm-package-manager.ts.

Not tested via linking and using in a terminal yet.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

Bun package manager is not supported.

What is the new behavior?

Adds support for Bun package manager. Falls back to npm commands when Bun does not have an analogous command, like search and view.

Implements NativeScript/NativeScript#10397

Migration steps

ns package-manager set bun, then use the ns CLI commands like normal.

[rigor789]

Marked this as experimental, so we can release it as-is and do follow-up adjustments as necessary.

[jasongitmail]

Great thanks!