WebAuthn Owner PoC For Safe

[nlordell]

This issue captures the work for vendoring a PoC ISignatureValidator implementation that supports WebAuthn.

Specifically, this should verify a WebAuthn signature matches a public key for some input hash.

Note that WebAuthn doesn't allow signing raw hashes, but an "envelope" instead. This needs to be decoded and verified as part of the process.

Existing implementations evaluated in #172 contain

Expected Output

1. Vendor a signer contract to the contracts/test directory
2. Unit test that verifies a UserOperation with a WebAuthn signer works over the EntryPoint
3. A test application that uses passkey to sign and execute a userop

[mmv08]

Just for the record, this issue has a lot of overlap with #173

We decided to pivot this PoC into a small web app that uses passkeys to learn more about WebAuthn as there are some peculiarities, such as it can only be used over HTTPS, you have to generate a user ID beforehand, etc.