only applies rules to the appropriate files

[brad-decker]

Previously the mocha rules were disabled for anything without the .test.js suffix, which unfortunately included the .spec.js files in E2E folder. This update aims to simplify overrides for tests by only extending the mocha configuration for files that need it.

Also, this change now only applies react rules to the UI folder.

[metamaskbot]

Builds ready [806a0cb]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• build viz: Build System
• code coverage: Report
• storybook: Storybook
• all artifacts

Page Load Metrics (640 ± 49 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	50	69	59	6	3
		domContentLoaded	358	826	638	102	49
		load	360	827	640	102	49
		domInteractive	358	825	638	102	49

[Gudahtt]

LGTM!