fix(testing): don't run tests against non-test files

[rwaskiewicz]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Unit tests (npm test) were run locally and passed
• E2E Tests (npm run test.karma.prod) were run locally and passed
• Prettier (npm run prettier) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

There are two issues that this PR solves (in 2 commits):

1. files that end with (test|spec|e2e).(js|ts|jsx|tsx) (without a period preceding any combination of that string) are picked up by the test runner - e.g. my-test.tsx will be picked up by the test runn
2. files that end in .j or .t will be picked up by the test runner

GitHub Issue Number: #3221

What is the new behavior?

I split the two issues solved here into two commits, and will likely 'rebase and merge' them. Each commit has a fix:

Commit 1: this commit adds test infrastructure for files picked up by jest for
testing purposes. because there is no efficient way to get the
interaction with stencil+jest (or any libary+jest for that matter) under test, we
instead extract the testRegex field out of the stencil TestConfig and
perform RegExp.test()-based assertions.

remove a single '?' from the testRegex field used that was making the
period preceding (test|spec|e2e) optional

Commit 2: update stencil's default testRegex to not capture .j and .t files

Does this introduce a breaking change?

• Yes
• No

Testing

First and foremost, unit tests were added and passed.

Next, I built Stencil on this branch (npm ci && npm run clean && npm run build). I then ran each of our test suites to verify we didn't regress in the number of tests we run on this branch vs main

• npm t
• npm run test.karma.prod
• npm run test.end-to-end

Finally, I npm packed the built artifact to test this on a Stencil project:

1. npm init stencil component my-cmp to generate a new Stencil project
2. cd my-cmp && npm i to get dependencies installed
3. npm t to get a baseline & verify that everything passed
4. npm run generate to generate a new component, my-test, accept default test files when prompted
5. npm run generate to generate a new component, my-e2e, accept default test files when prompted
6. npm run generate to generate a new component, my-spec, accept default test files when prompted
7. npm t to see that there are now failing tests for each of the new file
   
   s
8. npm i PATH_TO_TARBALL
9. npm t to see all tests pass and the created component files aren't pick up anymore