fix(relayer): save block by chain id

[cyberhorsey]

This PR fixes two issues:

1. Saving a block to the database should first check if a block height exists for that chain_id. Presently, it does not check fo chain_id, so now this can run synchronizing between both blocks.
2. Subscribe mode should not persist blocks saved to the database, in case you start it up in subscribe mode, but then still want to continue previously on the same database indexing the past in a separate instance fo the relayer.
3. Near-identical batch handling methods for when there are no events remaining have been combined.

[codecov]

Codecov Report

Merging #379 (90c64a9) into main (04702db) will decrease coverage by 0.29%.
The diff coverage is 50.90%.

@@            Coverage Diff             @@
##             main     #379      +/-   ##
==========================================
- Coverage   64.30%   64.00%   -0.30%     
==========================================
  Files          90       89       -1     
  Lines        2524     2492      -32     
  Branches      292      292              
==========================================
- Hits         1623     1595      -28     
- Misses        829      830       +1     
+ Partials       72       67       -5     

Flag	Coverage Δ		*Carryforward flag
bridge-ui	100.00% <ø> (ø)		Carriedforward from 1abacd5
protocol	59.00% <ø> (ø)		Carriedforward from 1abacd5
relayer	68.15% <50.90%> (-0.59%)	⬇️
ui	100.00% <ø> (ø)		Carriedforward from 1abacd5

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
packages/relayer/indexer/subscribe.go	82.75% <ø> (-3.73%)	⬇️
packages/relayer/indexer/filter_then_subscribe.go	20.25% <15.38%> (+0.25%)	⬆️
packages/relayer/indexer/service.go	75.00% <28.57%> (-4.32%)	⬇️
...er/indexer/set_initial_processing_block_by_mode.go	80.00% <60.00%> (-8.89%)	⬇️
packages/relayer/indexer/handle_event.go	50.00% <68.75%> (ø)
packages/relayer/cli/cli.go	61.18% <100.00%> (+0.16%)	⬆️
...kages/relayer/indexer/handle_no_events_in_batch.go	66.66% <100.00%> (-7.25%)	⬇️
packages/relayer/repo/block.go	76.92% <100.00%> (ø)
... and 1 more

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