Speed up karma runs for development

What does this MR do?

Make karma tests in watch mode run instantly. Don't include entire app when passing -f flag to karma.

Results

	Initial build	Rebuild	test_bundle Size
baseline	53s	21s	28.5MB
new	16s	3s	2.37MB
improvement	3.3x	7x	12x

test commands

time WEBPACK_REPORT=1 yarn karma -f *dashboard_spec.js	
WEBPACK_REPORT=1 yarn karma-start -f *dashboard_spec.js

other

• Web IDE tests are ~8MB because of monaco-editor. Still much faster than before

screenshots

before (includes everything):

after (includes mainly used):

Does this MR meet the acceptance criteria?

• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides