chore: add the new policy.json review process documentation and config

[naugtur]

Description

Introducing the document outlining policy review process.

The current change to CODEOWNERS doesn't remove the all devs group - this makes it a soft-launch of the process where a specific approving review is not yet mandatory.

We'll be releasing a training video early January

Related issues

Fixes: lack of attention to policy updates

Manual testing steps

1. Follow the process and experience joy

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.

[metamaskbot]

Builds ready [fe9af48]

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

Page Load Metrics (1558 ± 59 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	1363	2015	1561	132	64
		domContentLoaded	1348	1928	1529	120	58
		load	1367	1962	1558	122	59
		domInteractive	20	85	38	20	10
		backgroundConnect	10	63	29	19	9
		firstReactRender	15	73	32	22	11
		getState	4	49	12	12	6
		initialActions	0	0	0	0	0
		loadScripts	1001	1449	1148	90	43
		setupStore	6	20	8	3	1
		uiStartup	1518	2194	1757	130	62

Bundle size diffs

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