Fix debugging of TS Source so that breakpoints work when debugging the extension

[NullVoxPopuli]

Extracted from: #655

This change allowed me to place breakpoints in the TS/source, and have those breakpoints hit while the "Debug Extension" task is ran.

Nightly failures present on `main`

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Failed Tests 2 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

 FAIL  __tests__/cli/custom-extensions.test.ts > CLI: custom extensions > external file changes > adding a missing module
Error: Timed out waiting to see "Found 0 errors.". Instead saw: ""
 ❯ Timeout.<anonymous> ../../test-packages/test-utils/src/project.ts:229:10
    227|         detach();
    228|         reject(
    229|           new Error(
       |          ^
    230|             `Timed out waiting to see ${JSON.stringify(target)}. Instead saw: ${JSON.stringify(
    231|               output

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 FAIL  __tests__/cli/custom-extensions.test.ts > CLI: custom extensions > external file changes > removing an imported module
AssertionError: expected '\u001bc5:47:35 PM - File change detec…' to include 'Cannot find module \'./other\' or its…'
 ❯ __tests__/cli/custom-extensions.test.ts:119:21
    117| 
    118|       expect(output).toMatch('Found 1 error.');
    119|       expect(output).toMatch(
       |                     ^
    120|         "Cannot find module './other' or its corresponding type declarations."
    121|       );

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Test Files  1 failed | 23 passed (24)
     Tests  2 failed | 340 passed (342)
  Start at  17:46:59
  Duration  81.12s (transform 1.00s, setup 1ms, collect 22.40s, tests 387.23s)