contracts-bedrock: integrate GovernanceToken with Alligator

[0xfuturistic]

This PR implements the specs for GovernanceToken as defined in ethereum-optimism/specs#233.
Concretely, this allows accounts to be migrated to the Alligator, which holds the state and implements the advanced delegation logic on behalf of the GovernanceToken.

[semgrep-app]

Semgrep found 1 sol-style-return-arg-fmt finding:

• packages/contracts-bedrock/src/governance/Alligator.sol
  • L15 - Triage

Named return arguments to functions must be appended with an underscore (_)

_{Ignore this finding from sol-style-return-arg-fmt.}

Semgrep found 1 sol-style-input-arg-fmt finding:

• packages/contracts-bedrock/src/governance/Alligator.sol
  • L13 - Triage

Inputs to functions must be prepended with an underscore (_)

_{Ignore this finding from sol-style-input-arg-fmt.}

[semgrep-app]

Semgrep found 3 sol-style-notice-over-dev-natspec findings:

• packages/contracts-bedrock/src/governance/Alligator.sol
  • L174 - Triage
  • L267 - Triage
  • L268 - Triage

Prefer @notice over @dev in natspec comments

_{Ignore this finding from sol-style-notice-over-dev-natspec.}

Semgrep found 1 sol-style-input-arg-fmt finding:

• packages/contracts-bedrock/src/governance/Alligator.sol
  • L94 - Triage

Inputs to functions must be prepended with an underscore (_)

_{Ignore this finding from sol-style-input-arg-fmt.}

[semgrep-app]

Semgrep found 1 ban_non_wraparound_modifiers finding:

• packages/contracts-bedrock/src/governance/Alligator.sol
  • L93-94 - Triage

Modifiers that don't do something before and after execution are banned.

_{Ignore this finding from ban_non_wraparound_modifiers.}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 16.44%. Comparing base (4e20306) to head (c756097).

Additional details and impacted files

@@                 Coverage Diff                 @@
##           feat/gov-alligator   #11168   +/-   ##
===================================================
  Coverage               16.44%   16.44%           
===================================================
  Files                       8        8           
  Lines                     535      535           
  Branches                   71       71           
===================================================
  Hits                       88       88           
  Misses                    447      447           

Flag	Coverage Δ
chain-mon-tests	27.14% <ø> (ø)
sdk-tests	16.44% <ø> (ø)

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[cairoeth]

merging to #11167 so that it's easier to test both Alligator and GovernanceToken.