Refactor Contract Layout

[nlordell]

This PR changes the contract layout in the passkey package, as well as some small renames. It also changes constants to be used as library-ies instead of contracts that are inherited (to be more consistent, as both were used previously).

There are almost no logic changes, some notable examples that came with the refactor:

1. Since SignatureData needed to be shared by the WebAuthnSigner and WebAuthnSignerFactory, I created a WebAuthnSignature library that declares the stuck and includes the casting logic. This lead to some small changes in the WebAuthnSignerFactory notably to work around some "stack too deep" error that didn't happen before.
2. The WebAuthnConstants is now WebAuthnFlags and I removed the AUTH_DATA_FLAGS_BE and AUTH_DATA_FLAGS_BS because they aren't actual flags 🤷. Don't know how they got there, but the bits in those flags are officially reserved for future use. I also didn't bother adding the AT and ET flags, since those can't really be verified on-chain anyway and not really relevant from a signature verification perspective (they indicate what additional data is available in the authenticator data blob, but we don't make use of it anyway).

[akshay-ap]

lgtm

[coveralls]

Pull Request Test Coverage Report for Build 8328356680

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+62.4%) to 76.923%

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Totals
Change from base Build 8328333224:	62.4%
Covered Lines:	131
Relevant Lines:	155

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 8328356687

Details

• 1 of 24 (4.17%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 14.474%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
modules/passkey/contracts/WebAuthnSigner.sol	0	1	0.0%
modules/passkey/contracts/libraries/WebAuthnSignature.sol	0	1	0.0%
modules/passkey/contracts/4337/Safe256BitECSignerLaunchpad.sol	0	2	0.0%
modules/passkey/contracts/base/SignatureValidator.sol	0	2	0.0%
modules/passkey/contracts/verifiers/WebAuthnVerifier.sol	0	2	0.0%
modules/passkey/contracts/WebAuthnSignerFactory.sol	0	15	0.0%

Totals
Change from base Build 8328333224:	0.0%
Covered Lines:	17
Relevant Lines:	108

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💛 - Coveralls