add key literals to driver

[brad-decker]

This PR aims to improve the abstraction around sending keystrokes/values to input fields. The API aims to match playwright's implementation to allow a more straightforward migration in the near future. There are a few pieces:

1. Add the 'Key' constants to the driver itself, hardcoded instead of using selenium's. These can be later replaced with 'Enter' and 'Backspace' to match the playwright API for .press
2. Add driver.fill API to the driver that matches playwright's fill method. Fill differs from sendKeys in that it replaces the current value instead of adding to it.
3. Add driver.press API to the driver that matches playwright's press method. Playwright's implementation differs in that it expects key names like 'Enter' while selenium's expects unicode encoded key values.
4. Wraps all elements returned from driver with fill and press methods.

This PR includes the refactor to use these.

[metamaskbot]

Builds ready [fcee942]

• 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 (585 ± 50 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	47	85	58	9	4
		domContentLoaded	338	733	584	106	51
		load	340	733	585	105	50
		domInteractive	338	732	583	106	51

[Gudahtt]

LGTM! Apart from the conflicts. I can re-review after those are resolved.

[Gudahtt]

LGTM!

[metamaskbot]

Builds ready [467121c]

• 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 (634 ± 57 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	46	94	64	12	6
		domContentLoaded	351	770	633	118	57
		load	352	771	634	118	57
		domInteractive	351	769	633	118	57