Specify that Base is a multilayer network

[danyalprout]

Explanation

Currently we treat gas calculations differently for Optimism (example). As Base uses the op-stack, the logic for Optimism and Base should be the same. (e.g. the gas oracle is deployed on both networks)

Screenshots/Screencaps

No UI changes

Manual Testing Steps

• Open the extension
• Add the Base testnet
• Send some transactions

Pre-merge author checklist

• I've clearly explained:
  • What problem this PR is solving
  • How this problem was solved
  • How reviewers can test my changes
• Sufficient automated test coverage has been added

Pre-merge reviewer checklist

• Manual testing (e.g. pull and build branch, run in browser, test code being changed)
• PR is linked to the appropriate GitHub issue
• IF this PR fixes a bug in the release milestone, add this PR to the release milestone

If further QA is required (e.g. new feature, complex testing steps, large refactor), add the Extension QA Board label.

In this case, a QA Engineer approval will be be required.

[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

Merging #20097 (81ddaae) into develop (be469db) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop   #20097      +/-   ##
===========================================
- Coverage    69.43%   69.43%   -0.00%     
===========================================
  Files          990      990              
  Lines        37428    37434       +6     
  Branches     10039    10042       +3     
===========================================
+ Hits         25986    25990       +4     
- Misses       11442    11444       +2     

Impacted Files	Coverage Δ
shared/constants/network.ts	100.00% <ø> (ø)
ui/selectors/selectors.js	86.68% <100.00%> (+0.13%)	⬆️

... and 2 files with indirect coverage changes

[danjm]

LGTM

[smallbraingames]

Hello, I was wondering if there are any blockers to merge I can help with? Users are paying 10x gas they need to currently.

Also in the meantime are there comms I could share?