Abstract test snapshot builder into class

[dplain90]

As a VSCode Programming Language Extension creator I want to test my tmLanguage file using the TypeScript-TmLanguage test suite to ensure my extension supports all future and current TS language use-cases.

This is not possible in it's current state as the snapshot build script has hardcoded file names and config settings.

This PR does the following:

• Refactors tests/build.ts into a Builder class tests/builder.ts which can be passed configuration options

• Uses a Builder instance in tests/test.ts to generate scopes

[msftclas]

All CLA requirements met.

[sheetalkamat]

Please do not change file names and also do not convert to class, You can always use function instead.