glint cli does not produce declaration-related errors where tsc cli does

[bendemboski]

Repro

1. mkdir glint-test && cd glint-test
2. yarn init -y
3. yarn add --dev typescript @glint/core @glint/template @glint/environment-ember-loose (same behavior if you install the 1.0 beta)
4. Create a tsconfig.json that looks like:

   {
   "compilerOptions": {
   "declaration": true,
   },
   "glint": {
   "environment": "ember-loose"
   }
   }

5. Create a foo.ts that looks like:

   
   class Foo {
   protected prop = 1;
   }

export default function makeBar() { class Bar extends Foo {} return new Bar(); }

10. Run `yarn tsc` and `yarn glint`

## Expected

`yarn glint` produces the same errors as `yarn tsc`

## Actual

`yarn tsc` errors with `foo.ts:5:25 - error TS4094: Property 'prop' of exported class expression may not be private or protected` while `yarn glint` produces no errors.

## Discussion

I'm not 100% sure this is an issue that GLint should address, but it seems worth raising. We _could_ choose to assert that `glint` should always produce a superset of the errors that `tsc` produces, i.e. it produces all the same errors for typescript, plus additional errors for templates. If so, then it's failing to do so in this case.

I kind of think that the line at the GLint overview documentation that states that `Glint's CLI provides a template-aware tool for performing end-to-end TypeScript typechecking on your project` implies that we should be/are making this assertion, but I also recognize that this is a bit of an edge case.