fix: allow onboarding and unlocking wallet without Infura mainnet connectivity

[legobeat]

Description

Fixes issue where custom networks are not configurable until after wallet is unlocked.

Related issues

• Resolves [Bug]: Can not add custom network during onboarding #23333
• Fix "User can add custom network during onboarding" flaky tests #22713
• Origin: Fix #20274 - Update locked network menu controls #20277

Manual testing steps

0. Fresh wallet, disconnect internet, custom RPC node
1. Open MetaMask
2. Add custom RPC node
3. Complete onboarding

Screenshots/Recordings

Before

no-add-network-p.mp4

After

can-add-network-p.mp4

Pre-merge author checklist

• I’ve followed MetaMask Coding Standards.
• I've clearly explained what problem this PR is solving and how it is solved.
• I've linked related issues
• I've included manual testing steps
• I've included screenshots/recordings if applicable
• 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 properly set the pull request status:
  • In case it's not yet "ready for review", I've set it to "draft".
  • In case it's "ready for review", I've changed it from "draft" to "non-draft".

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.72%. Comparing base (6e397d0) to head (4ebb6fd).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #23388      +/-   ##
===========================================
- Coverage    68.72%   68.72%   -0.00%     
===========================================
  Files         1124     1124              
  Lines        43606    43605       -1     
  Branches     11669    11668       -1     
===========================================
- Hits         29967    29965       -2     
- Misses       13639    13640       +1     

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[metamaskbot]

No release label on PR. Adding release label release-11.14.0 on PR, as PR was added to branch 11.14.0 when release was cut.