feat: add auto sign-in for existing users

[mathieuartu]

Description

This PR adds an auto-sign-in mechanism.
Currently, users that upgraded from a pre-auth era version might meet the conditions for being signed-in, but aren't because we attached the sign-in mechanism to manual actions like toggling MetaMetrics or Profile Syncing.
This fixes that, by checking if conditions for signing-in are met every time the UI opens, and if so, dispatching the sign-in method from AuthenticationController

Related issues

Fixes:

Manual testing steps

1. Go to this page...

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: app/scripts/background.js

Function	Unhandled Issue
setupController	Error: NetworkController state is invalid: selectedNetworkClientId '3938de10-581d-4264-b8b0-51d33ce001... ... Event Count: 27 Affected Users: 0

---

_{Did you find this useful? React with a 👍 or 👎}

[metamaskbot]

Builds ready [b83be71]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1757 ± 66 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	1560	2003	1761	139	67
		domContentLoaded	1548	1990	1710	136	65
		load	1557	2005	1757	137	66
		domInteractive	26	69	36	14	6
		backgroundConnect	9	159	44	39	19
		firstReactRender	16	114	51	34	16
		getState	5	66	21	18	9
		initialActions	0	1	0	0	0
		loadScripts	1114	1466	1276	103	49
		setupStore	6	86	14	19	9
		uiStartup	1792	2686	2144	291	140

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

• background: 918 Bytes (0.02%)
• ui: 0 Bytes (0.00%)
• common: 0 Bytes (0.00%)