feat: graceful and alertable relayer reorg detection

[tkporter]

Description

• Only panics in the validator if there is a reorg detected
• Mostly solves https://github.com/hyperlane-xyz/issues/issues/1394 (does not have super clear alert conditions for a reorg occurring, this should come later)
• Whereas before we would use Result<Option<Vec<u8>> as a return type for metadata building, where the Result indicates some error occurred (e.g. an RPC issue or something), Ok(Some(_)) meant that metadata building was successful, and Ok(None) meant that no error occurred but simply that fetching metadata wasn't successful -- we now have a new Metadata enum:

#[derive(Clone, Debug)]
pub enum Metadata {
    /// Able to fetch metadata
    Ok(Vec<u8>),
    /// Unable to fetch metadata, but no error occurred
    CouldNotFetch,
    /// While building metadata, encountered something that should
    /// prohibit all metadata for the message from being built.
    /// Provides the reason for the refusal.
    Refused(String),
}

• When we are building metadata and encounter a reorg flag in a validator that's used by the message, we handle this and return Metadata::MetadataBuildingRefused. The aggregation ISM will propagate this to make sure that we have end behavior of flatly refusing to build metadata for a message even if a nested metadata builder encounters this. If this happens, a new reprepare reason MessageMetadataRefused is introduced that's used.
• e2e test is added to confirm this behavior

Drive-by changes

Related issues

Backward compatibility

Testing

e2e, some unit

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.53%. Comparing base (ff874be) to head (420b059).
Report is 13 commits behind head on main.

Additional details and impacted files

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  Coverage   77.53%   77.53%           
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  Files         103      103           
  Lines        2110     2110           
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Components	Coverage Δ
core	87.80% <ø> (ø)
hooks	79.39% <ø> (ø)
isms	83.68% <ø> (ø)
token	91.27% <ø> (ø)
middlewares	79.80% <ø> (ø)