[Bug] eip7840 BlobParams SerdeHelper drops two fields

### Component

serde

### What version of Alloy are you on?

1.0.41

### Operating System

None

### Describe the bug

Serde round-trip for a BlobParams instance is broken:
https://www.diffchecker.com/BcFU5LmK/

`max_blobs_per_tx` gets set to `max_blob_count`, while `blob_base_cost` is always set to zero because this behavior is hardcoded in the SerdeHelper:

https://github.com/alloy-rs/alloy/blob/c1987556cdcd0e99a1ce9c6512a8eea800df34fa/crates/eips/src/eip7840.rs#L219-L220