Expose moon_getLatestSyncedBlock RPC endpoint

[gonzamontiel]

What does it do?

• Exposes an RPC endpoint on moon_getLatestSyncedBlock
• Returns the latest synced block number

What important points reviewers should know?

• I included it in the finality rpc module since it looked somehow appropriate.

Is there something left for follow-up PRs?

What alternative implementations were considered?

Are there relevant PRs or issues in other repositories (Substrate, Polkadot, Frontier, Cumulus)?

Is blocked by moonbeam-foundation/frontier#218

What value does it bring to the blockchain users?

[github-actions]

Coverage Report

@@                        Coverage Diff                        @@
##           master   gonza-rpc-latest-synced-block      +/-   ##
=================================================================
+ Coverage   81.10%                          81.33%   +0.23%     
+ Files         274                             301      +27     
+ Lines       80566                           85711    +5145     
=================================================================
+ Hits        65343                           69709    +4366     
+ Misses      15223                           16002     +779     

Files Changed	Coverage
/client/rpc/finality/src/lib.rs	88.14% (-7.78%)	🔽
/pallets/parachain-staking/src/lib.rs	91.73% (-0.01%)	🔽
/pallets/parachain-staking/src/mock.rs	97.65% (+0.02%)	🔼
/pallets/parachain-staking/src/tests.rs	91.39% (+0.03%)	🔼
/precompiles/xcm-transactor/src/v1/mod.rs	87.95% (+0.45%)	🔼
/precompiles/xcm-transactor/src/v2/mod.rs	76.42% (-2.22%)	🔽
/precompiles/xcm-transactor/src/v3/mod.rs	83.33% (-2.26%)	🔽
/precompiles/xcm-utils/src/lib.rs	90.98% (-0.69%)	🔽

Coverage generated Wed Jul 10 09:07:35 UTC 2024