Fix doc MyGovernor example doesn't compile

[qiweiii]

Fixes #4278

• Put code snippet in contracts/mocks/docs so it can be checked for compilation errors.
• Added cancel function that is missing

function cancel(
    address[] memory targets,
    uint256[] memory values,
    bytes[] memory calldatas,
    bytes32 descriptionHash
) public override(Governor, GovernorCompatibilityBravo, IGovernor) returns (uint256) {
    return super.cancel(targets, values, calldatas, descriptionHash);
}

PR Checklist

• Tests
• Documentation
• Changeset entry (run npx changeset add)

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[frangio]

Thank you @qiweiii! Would you mind doing the same for the other Solidity contracts in governance.adoc?

[qiweiii]

Yea, happy to do it

[qiweiii]

@frangio Just added other solidity contract example, but I have a few concerns:

1. example contract naming could be confusing in future if move more example under contracts/mocks/docs, for example, there would be many MyToken in docs, instead of naming them MyToken1, MyToken2, do you think specific name like MyTokenGovernance could be better?
2. example code format is changed by solidity code formatter, after putting them in .sol file

function _mint(address to, uint256 amount)
        internal
        override(ERC20, ERC20Votes)
    {
        super._mint(to, amount);
    }

is changed to

function _mint(address to, uint256 amount) internal override(ERC20, ERC20Votes) {
    super._mint(to, amount);
}

making the line a bit longer, user will need to scroll in order to read, is this acceptable?

[frangio]

1. Perhaps we can put them under mocks/docs/governance/ to disambiguate that they are for the governance article. MyTokenGovernance is not necessary then. But it would still make sense to have different names that refer to the specific thing the example is showcasing.
2. Oh, this is not ideal but I don't know how to fix it so for now let's just accept what the formatter wants.

[frangio]

I realized mocks/docs/governance/ would not have worked with one of our scripts so I pushed a commit to fix that.

[qiweiii]

we can put them under mocks/docs/governance/ to disambiguate that they are for the governance article.

Good idea!
I have put them under /governance, do you think the new contract names are good?

[qiweiii]

test-upgradable failed:

<--- Last few GCs --->

[1930:0x4e72540]  1644838 ms: Scavenge (reduce) 4063.6 (4098.7) -> 4062.7 (4098.7) MB, 8.4 / 0.0 ms  (average mu = 0.369, current mu = 0.359) allocation failure 
[1930:0x4e72540]  1644943 ms: Scavenge (reduce) 4063.6 (4095.7) -> 4062.7 (4096.7) MB, 18.3 / 0.0 ms  (average mu = 0.369, current mu = 0.359) allocation failure 
[1930:0x4e72540]  1645059 ms: Scavenge (reduce) 4063.7 (4095.7) -> 4062.7 (4096.7) MB, 11.3 / 0.0 ms  (average mu = 0.369, current mu = 0.359) allocation failure 


<--- JS stacktrace --->

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory

do we need to increase the --max_old_space_size?

# .github/workflows/checks.yml
- NODE_OPTIONS: --max_old_space_size=4096
+ NODE_OPTIONS: --max_old_space_size=5120

[frangio]

I've retargeted the branch to release-v4.9 and rebased on top of that because there are some new changes in master that affect this and we will want to update separately. I will open a separate PR to include the changes in master.

Thank you so much!

[Amxx]

This PR includes some changes to ERC721Consecutive (the offset part). I'm not sure its intentional. I also don't think it should be the case.

Bad changes in PR

[frangio]

My bad, happened when I rebased... Will fix later.

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