chore: Refactor offscreen creation logic

[FrederikBolding]

Description

Refactor initialization logic to defer creation of the offscreen document until the MetaMaskController is initialized. This adds a offscreenPromise to the controller that can be awaited for functionality that requires the offscreen document to be created.

Additionally this PR adds a message that the offscreen document will send once initial execution of the offscreen page has finished. This is awaited in the offscreenPromise.

We await offscreenPromise before unlocking the keyrings as some keyrings rely on the offscreen document to process requests, e.g. hardware wallets.

There may be room for more improvements here though, that I have not tackled in this PR. As the hardware wallet logic doesn't seem to wait for iframes to fully load, so there is a chance of some missed messages.

I have tested that hardware wallet support, at least for Ledger, is still working following the changes in this PR.

[metamaskbot]

Builds ready [219ff99]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
  • content-script: 0
  • offscreen: 0
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (173 ± 247 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	70	253	99	37	18
		domContentLoaded	10	27	13	4	2
		load	45	2410	173	513	247
		domInteractive	10	27	13	4	2

Bundle size diffs [🚨 Warning! Bundle size has increased!]

• background: 1.16 KiB (0.03%)
• ui: 0 Bytes (0.00%)
• common: 28 Bytes (0.00%)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.41%. Comparing base (68d35f0) to head (bf601f7).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #25302      +/-   ##
===========================================
- Coverage    65.42%   65.41%   -0.01%     
===========================================
  Files         1381     1381              
  Lines        54695    54711      +16     
  Branches     14340    14351      +11     
===========================================
+ Hits         35779    35786       +7     
- Misses       18916    18925       +9     

☔ View full report in Codecov by Sentry.
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[Gudahtt]

LGTM!

[metamaskbot]

Builds ready [bf601f7]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
  • content-script: 0
  • offscreen: 0
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (51 ± 3 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	67	105	85	9	4
		domContentLoaded	9	22	12	3	1
		load	42	64	51	6	3
		domInteractive	9	22	12	3	1

Bundle size diffs [🚨 Warning! Bundle size has increased!]

• background: 1.26 KiB (0.04%)
• ui: 0 Bytes (0.00%)
• common: 28 Bytes (0.00%)

[metamaskbot]

Missing release label release-12.0.0 on PR. Adding release label release-12.0.0 on PR and removing other release labels(release-12.1.0), as PR was cherry-picked in branch 12.0.0.