fix: fall back to bundled chainlist

[legobeat]

Description

The list of known chains is fetched at runtime from https://chainid.network/chains.json and cached. There are some issues with the way this works:

• MetaMask will not have a list of chains until online (if ever)
• When the 24h cache timeout expires, the chainlist becomes unavailable

This PR addresses this by:

• Refactoring out https://chainid.network/chains.json into constant CHAIN_SPEC_URL
• Add new optional option allowStale to fetchWithCache. If set to true, it will falling back to return any entry instead of throwing an error when a request fail.
• Set allowStale to true for all requests to CHAIN_SPEC_URL
• Seed the fetch cache for CHAIN_SPEC_URL with eth-chainlist, which is the same data exposed via a published npm package.
  • Open for suggestions on if this should be bundled differently - maybe we want our own equivalent mirror?

While an improvement, this could still be further improved.

• The bundled result could be used immediately in all cases without waiting for response
• The cached data could be updated asynchronously in the background, without being prompted by user action

I currently consider these out-of-scope for this PR.

Or put more generally: Decoupling the fetching of the data from its use would be even better.

Related issues

Fixes:

Manual testing steps

1. Go to this page...

Screenshots/Recordings

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After

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[codecov]

Codecov Report

Attention: Patch coverage is 73.33333% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 65.99%. Comparing base (df218fa) to head (a7e126f).

Files	Patch %	Lines
app/scripts/metamask-controller.js	77.78%	2 Missing ⚠️
shared/lib/fetch-with-cache.ts	60.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #23392      +/-   ##
===========================================
- Coverage    66.00%   65.99%   -0.00%     
===========================================
  Files         1348     1348              
  Lines        52503    52512       +9     
  Branches     13494    13492       -2     
===========================================
+ Hits         34651    34655       +4     
- Misses       17852    17857       +5     

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[naugtur]

things to consider here:

• bundle size may be a concern (0.5MB package size)
• security concern - what's the risk of it containing malformed or malicious data?

possible alternatives:

• ship our own copy of current state of the online endpoint and put it in MM as an asset or as a package we publish ourselves.

@Gudahtt any ideas who's owning this bit and could have opinions?