feat: Add experimental provider request RPC method

[FrederikBolding]

Adds an experimental RPC method that lets Snaps make requests to networks that are not currently selected in the MetaMask UI. This is a large improvement for Snaps that want to leverage MetaMask RPC as previously the only access to RPC was given through endowment:ethereum-provider which strictly uses the currently selected network. This change would effectively let Snaps make requests to any networks added by the user and is a temporary stopgap solution until the MetaMask multichain API ships. This means that this API may break at any time, use accordingly.

Snaps with endowment:ethereum-provider would now be able to make requests like this:

const chainId = await snap.request({
  method: 'snap_experimentalProviderRequest',
  params: {
    chainId: 'eip155:59144',
    request: { method: 'eth_chainId' },
  },
});

The RPC method requires the endowment:ethereum-provider permission and enforces an allowlist to only allow access to certain RPC methods (mostly read methods).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.43%. Comparing base (24e7f90) to head (7ede87f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2773      +/-   ##
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+ Coverage   94.41%   94.43%   +0.01%     
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  Files         482      483       +1     
  Lines       10261    10297      +36     
  Branches     1563     1568       +5     
==========================================
+ Hits         9688     9724      +36     
  Misses        573      573              

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