Enrich `GetImmutableBlockPointError` with an error variant for invalid hash size, so `ouroboros-consensus` can properly validate `RawBlockHash` size

[tbagrel1]

The getImmutableBlockPoint callback in Cardano.Network.LedgerPeerConsensusInterface.LedgerPeersConsensusInterface receives a Point RawBlockHash, where RawBlockHash wraps a ShortByteString of arbitrary length apparently.

On the consensus side, in ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Node.hs, when we use getImmutableBlockPoint, we have to convert that raw hash into a block-specific HeaderHash blk. Previously ConvertRawHash was very lax about hash length, and hashSize value was not enforced by conversion methods from/to HeaderHash.

With [Peras 25.5] PR we are improving the ConvertRawHash class to be more explicit about expected hash length, and ensure the hash length invariant is respected during conversions (FTR, the old functions are still available but have been prefixed by unsafe to indicate that they do not enforce the invariant).

So, ideally, in getImmutableBlockPoint, when the RawBlockHash size doesn't match the expected one for HeaderHash blk, we would like to be able to return a proper error value instead of a fatal error.

Suggestion

Add a constructor ImmutableBlockInvalidHashSize Int Int to GetImmutableBlockPointError type in Cardano.Network.LedgerPeerConsensusInterface