Detect issues in parent initializer calls

[ericglau]

Reports if a contract is non-abstract and any of the following are true:

1. Missing initializer: This contract does not appear to have an initializer, but parent contracts require initialization.
2. Missing initializer call: This contract's initializer is missing a call to a parent initializer.
3. Duplicate initializer call: This contract has duplicate calls to the same parent initializer function.
4. Incorrect initializer order (warning): This contract does not call parent initializers in the correct order.

Note that reinitializers will be ignored for these validations.

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Future improvements:

• Allow users to annotate that a function is an initializer - see Detect issues in parent initializer calls #1095 (comment)
• Warn that reinitializers (if detected) are not included in validations
• Transitive parents are treated as not requiring initialization if a parent initializer calls them. This PR checks that the remaining parent contracts are initialized, but some parent contracts could have multiple initializer functions, where not all of those functions actually initialize their transitive parents. Add tracking of which specific parent initializers are called, so the rest's transitive parent calls can be reported as missing.

Fixes #160

[ernestognw]

For another PR, I think it may be useful if we annotate initializers with @custom:initializer or similar.
The idea is that there are contracts with initializers that don't follow the initialize or initializer convention in its name.

A concrete example is any of the Signers we created for ERC4337 accounts:

abstract contract SignerRSA is AbstractSigner {
    error SignerRSAUninitializedSigner(bytes e, bytes n);

    bytes private _e;
    bytes private _n;

    /// @custom:initializer true
    function _initializeSigner(bytes memory e, bytes memory n) internal {
        if (_e.length != 0 || _n.length != 0) revert SignerRSAUninitializedSigner(e, n);
        _e = e;
        _n = n;
    }

...
}

[ericglau]

Added recursive checks in the initializer function, to detect cases where its called functions (e.g. helper functions or parent initializer calls) may have duplicate calls or incorrect order of calls to parent initializers.