feat(rpc): Modify getL1Message* rpc to acces L1MesageKey

[varun-doshi]

Fixes #372

• get_l1_message_by_index now takes a L1MessageKey instead of an index: u64
• GetL1MessageByIndex under DatabaseQuery takes a L1MessageKey

[frisitano]

Thanks for your contribution! I've added a few comments inline. Additionally, it would be great if we could add a few tests:

• One round trip of any vairant (serialize and then deserialze)
• One or two hand crafted serialized instances and then deserialize to ensure we can construct the correct enum variant. This gives us confidence in the rpc API we can expect.

[codspeed-hq]

CodSpeed Performance Report

Merging #378 will not alter performance

_{Comparing varun-doshi:varun/get-l1-msg (f0f9e4f) with main (f64369c)}

Summary

✅ 2 untouched

[frisitano]

thanks! lgtm