Refactored code to make use of interface generics from monaco-editor

[bkataru]

Refactored MonacoInlineCompletion into its own file to reuse the class to redefine some interfaces as interface generics in accordance with the monaco-editor API because MonacoInlineCompletion is after all an implementation of the monaco.languages.InlineCompletion interface.

Also added the following type-guard for inlineCompletionItems to remove the type assertion as monaco.languages.InlineCompletion[]

      .filter(
        (item?: MonacoInlineCompletion): item is MonacoInlineCompletion =>
          !!item
      );

[andyzg]

Thank you for the refactor! Left one comment, and then I can test this and get this merged!

[andyzg]

What's the reason for changing the module resolution to Bundler?