Precompile all frontend test fixtures

What does this MR do?

Compiles all static JavaScript fixtures within the rake teaspoon:fixtures task in order to ease the transition away from the Teaspoon testing suite. See issue #26226 (closed)

Also converts all calls to teaspoon built-in functions (fixture.preload(), fixture.load(), fixture.set()) to those used by the jasmine library itself to further reduce dependence on Teaspoon.

Are there points in the code the reviewer needs to double check?

Ensure no fixture.load() method calls still point to the old locations... They will still work for now, but will break when we ditch Teaspoon. I think I got all of them.

Why was this MR needed?

Karma cannot compile HAML fixtures on the fly, so a precompile step is required. Also Karma does not recognize teaspoon's built-in helper methods.

Does this MR meet the acceptance criteria?

• Changelog entry added
• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #26226 (closed)