Add web3 shim usage notification

[rekmarks]

Implements the web3 shim usage notification, using the AlertController and HomeNotification. The new notification has been tested in Firefox and Chrome.

The web3 shim usage logging state now lives in the alert controller. Its lifecycle is coterminous with the extension background process, as it's erased on boot. The notification is shown in the popup only if the current website has any permissions and attempted to use web3. The user can:

1. Ignore the notification
2. Dismiss the notification. This will hide the notification for the current website until the extension is restarted.
3. Select "Don't show this again", and dismiss the notification. This will hide the notification for all websites until the user re-enables it in settings. A tooltip indicates this possibility to the user.

In sum, the following changes were made:

• Moves the alert controller constants to shared/constants/alerts, adds new constants
• Adds new messages
• Adds relevant state and methods to the alert controller
• Fixes alert controller state initialization bug
  • The persisted would overwrite defaultState.alertEnabledness rather than merging it, meaning that new alerts wouldn't be added to state. This hasn't bitten us because the only other alert added since the controller was created can't be toggled.
• Adds relevant selectors and actions in the UI
• Adds a checkbox to the HomeNotification component, which is used for disabling the alert
• Adds a link to a support article (yet to be published) in the web3 shim usage notification
• Deletes app/images/icons/connect.svg, which we missed deleting in Disable console in contentscript #10040

[metamaskbot]

Builds ready [26c9536]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (597 ± 24 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	32	78	47	11	5
		domContentLoaded	530	714	596	51	24
		load	532	715	597	50	24
		domInteractive	530	713	596	51	24

[metamaskbot]

Builds ready [b7b3d3f]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (550 ± 11 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	32	60	45	9	4
		domContentLoaded	511	588	548	22	11
		load	513	589	550	22	11
		domInteractive	511	588	548	22	11

[brad-decker]

Q: should you just spread ...defaultState before alertEnabledness and remove the empty objects here? That way if default state changes in the future it is easily extensible here? No strong opinions on this, it is safe the way it is.

[brad-decker]

actually, in retrospect -- do we want persistence for web3ShimUsageOrigins? Then we'd want to spread initState.web3ShimUsageOrigins into the state declaration

[rekmarks]

We don't want to persist web3ShimUsageOrigins, because we want dismissed web3 shim usage notifications to reappear if the extension is restarted (assuming the notification is enabled), and storing the origins could contribute to state bloat over time.

Nevertheless, I followed your suggestion about spreading defaultState first, it's better!

[metamaskbot]

Builds ready [995f518]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (507 ± 29 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	31	61	44	9	4
		domContentLoaded	306	557	506	60	29
		load	308	559	507	61	29
		domInteractive	306	556	505	60	29

[metamaskbot]

Builds ready [6fd5a07]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (601 ± 33 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	34	80	51	13	6
		domContentLoaded	501	750	599	69	33
		load	506	751	601	69	33
		domInteractive	501	749	599	69	33

[brad-decker]

LGTM

[metamaskbot]

Builds ready [4cb4bfa]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (545 ± 12 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	32	60	45	10	5
		domContentLoaded	508	619	543	24	12
		load	510	620	545	24	12
		domInteractive	508	619	543	24	12