feat: bundler config

[NathanWalker]

PR Checklist

• [x] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• [x] 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.
• [x] 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
• [ ] Add test for default bundler param in projectConfigService
• [ ] Add test for all BundlerCompilerService bundlers

What is the current behavior?

Webpack bundler was the only supported bundling option.

What is the new behavior?

This introduces the ability to specify a bundler in nativescript.config:

bundler: 'webpack' | 'rspack' | 'vite' 

It deprecates webpackConfigPath (will always be supported though) in favor of bundlerConfigPath to specify location of the config associated with the defined bundler.

https://github.com/NativeScript/nativescript-cli/issues/5836