chore: cp-12.18.0 - Remove MULTICHAIN_API feature flag and expose Multichain API on all build types (#32351) Cherry-pick

[DDDDDanica]

Previously the Multichain API was only available on Flask and Beta builds. Starting in 12.18.0 we are releasing the Multichain API to all build types including stable

Cherry-pick: https://github.com/MetaMask/metamask-extension/pull/32351/files
Fixes: https://github.com/MetaMask/MetaMask-planning/issues/4779

1. Build this branch in a normal stable build (yarn start)
2. Go to https://metamask.github.io/test-dapp-multichain/latest/
3. Enter your extensionId (watch video below to see where) -> Detection on stable blocked by 22.1.0 providers#420
4. See that you're able to connect and interact with the multichain api

Screen.Recording.2025-04-28.at.2.44.45.PM.mov

Screen.Recording.2025-04-28.at.3.50.31.PM.mov

• 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.

• 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.

---

Description

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.

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​metamask/​providers@​22.0.1 ⏵ 22.1.0				+1

View full report

[metamaskbot]

Builds ready [dffde0b]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• bundle size: Bundle Size Stats
• user-actions-benchmark: User Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all CircleCI artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7, 8
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

UI Startup Metrics (1193 ± 55 ms)

Platform	BuildType	Page	Metric	Mean (ms)	Min (ms)	Max (ms)	Std Dev (ms)	P 75 (ms)	P 95 (ms)
Chrome	Browserify	Home	uiStartup	1193	1080	1334	55	1234	1286
			load	1040	939	1175	54	1089	1133
			domContentLoaded	1035	931	1170	54	1081	1127
			domInteractive	16	13	43	5	16	27
			firstPaint	712	135	1176	411	1053	1114
			backgroundConnect	6	3	11	1	7	9
			firstReactRender	20	15	46	5	21	34
			getState	12	5	35	7	16	30
			initialActions	0	0	1	0	0	1
			loadScripts	798	675	937	52	838	876
			setupStore	7	4	19	2	7	13
	Webpack	Home	uiStartup	2139	1750	2468	172	2262	2406
			load	1678	1352	2003	137	1766	1889
			domContentLoaded	1672	1349	1998	137	1760	1886
			domInteractive	16	11	57	10	14	45
			firstPaint	189	66	391	75	247	331
			backgroundConnect	26	9	89	14	30	53
			firstReactRender	192	53	384	118	307	355
			getState	12	3	172	17	12	27
			initialActions	3	1	8	1	3	6
			loadScripts	1667	1344	1974	137	1757	1876
			setupStore	20	7	199	26	21	41
Firefox	Browserify	Home	uiStartup	1368	1198	1771	107	1411	1601
			load	1219	1038	1642	108	1276	1428
			domContentLoaded	1219	1038	1642	108	1276	1428
			domInteractive	105	39	243	31	116	162
			firstPaint	NaN	NaN	NaN	NaN	NaN	NaN
			backgroundConnect	21	13	107	11	21	37
			firstReactRender	22	20	34	3	23	29
			getState	9	4	183	18	8	18
			initialActions	0	0	5	1	0	1
			loadScripts	1200	1024	1628	107	1262	1409
			setupStore	6	4	24	3	6	8
	Webpack	Home	uiStartup	1484	1332	1880	108	1550	1707
			load	1273	1156	1579	91	1318	1456
			domContentLoaded	1273	1155	1579	91	1317	1455
			domInteractive	82	57	227	23	90	126
			firstPaint	NaN	NaN	NaN	NaN	NaN	NaN
			backgroundConnect	21	14	60	6	23	28
			firstReactRender	34	28	55	5	36	46
			getState	12	4	303	30	9	29
			initialActions	1	0	2	1	1	1
			loadScripts	1254	1140	1558	90	1296	1434
			setupStore	8	5	45	4	8	11