feature(crosschain resolver): simplify reverse resolver

[TateB]

changes:

• SignatureReverseResolver
  • removed setText* functions
  • removed versionable records
    • no longer required without setText, since there is only one field set
  • removed clearRecords functions
    • no longer required without record versioning
  • optimisation: removed usage of authorisedSignature modifier and isAuthorisedWithSignature func, switched to inline
    • isAuthorisedWithSignature used in the authorisedSignature modifier required node for the address which was calculated within the function itself. node however was also used elsewhere in subsequent execution outside the modifier, and since modifiers can't return values it was unreachable. initially switched to just calling the isAuthorisedWithSignature function inline, but it's only used once now (from the removal of setText/clearRecords), so it's just inline.
  • optimisation: changed signature structure to remove the usage of the double-hashed function selector/name (i.e. bytes32 id replaced with bytes4, string)
    • not really sure why it was like this in the first place?
  • optimisation: inceptionDate now in seconds (to align with block timestamp) instead of milliseconds
    • previously afaik ms was a requirement because of multicalls and subsequent calls within the same block, but now that's no longer really useful
  • optimisation: name variable as calldata instead of memory
• L2ReverseResolver
  • optimisation: removed use of ownerAndAuthorisedWithSignature modifier function, logic now inline
  • optimisation: name variable as calldata instead of memory
  • optimisation: inceptionDate now in seconds
• ReverseRegistrar
  • removed relayer argument in setNameForAddrWithSignature and claimForAddrWithSignature
    • it was redundant since we check that the relayer is msg.sender anyway, and if msg.sender isn't the relayer variable the signed message won't be verified
  • optimisation: name variable as calldata instead of memory
• added ts tests
• added license to contracts
• moved sha3HexAddress func from LowLevelCallUtils lib to standalone AddressUtils
  • there was no overlap in usage of that function and the rest of the library, and the function alone isn't really a low level call utility func