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

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]](https://github.com/IntersectMBO/ouroboros-consensus/pull/2033) 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`

Start in Cardano.Network.LedgerPeerConsensusInterface by reading GetImmutableBlockPointError and the getImmutableBlockPoint callback, then inspect its use in ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Node.hs. Add the suggested invalid-hash-size error variant so a RawBlockHash size mismatch can be returned as an error rather than a fatal error.

Written by the indexing model from the issue text.