[feat][lsp] add support for custom config file name(s)

[mjames-c]

The tsgo LSP is currently hardcoded to look for tsconfig.json files for figuring out project configuration for a given source file (similar to TSv5). My request is to make the config file names the LSP searches for configurable (e.g. a vscode option like typescript.native-preview.configNames: string[])

This would allow my company (Canva) to experiment and incrementally rollout different project configurations to our 600+ frontend engineers. If the TS team is onboard with this feature being added it's something my team could contribute. Thanks!