Events db backend

[psheth9]

This PR consolidates all the events related changes into single one !!

Add Events Schema: #192
Refactor getEvents #215
Fix migration failures (#262)

Overall design:

• Ingest events into DB: store entire eventXDR along with metadata like contract_ids, topics etc..
• Combine contract_ids and topics from all the filters for a given request and pass it along to DB (to save multiple DB calls)
• Fetch events and apply filter again based on the request (on less data comparatively)

Other Refactor:

• Remove in-memory events store
• Introduce endLedgerSeq
• Add migration related logic for events

Data Flow:

Design Docs:

• Eng doc

• Benchmarking doc here

Parent Epic #115
Fixes: #190

[aditya1702]

Great job!!

[Shaptic]

So stoked to see this getting closer to the finish line 👏

Buuuuut here's another comment dump 😝

[psheth9]

  Running [/home/runner/golangci-lint-1.59.1-linux-amd64/golangci-lint run --new-from-patch=/tmp/tmp-4738-XJ8wnGKFOZhU/pull.patch --new=false --new-from-rev=] in [/home/runner/work/soroban-rpc/soroban-rpc] ...
  Error: cmd/soroban-rpc/internal/db/event.go:236:27: fmt.Errorf can be replaced with errors.New (perfsprint)
  		return errors.Join(err, fmt.Errorf("db read failed for requested parameter"))
  		                        ^
  Error: cmd/soroban-rpc/internal/db/event.go:260:28: fmt.Errorf can be replaced with errors.New (perfsprint)
  			return errors.Join(err, fmt.Errorf("failed to parse cursor"))
  			                        ^
  Error: cmd/soroban-rpc/internal/db/event.go:266:28: fmt.Errorf can be replaced with errors.New (perfsprint)
  			return errors.Join(err, fmt.Errorf("failed to decode event"))
  			                        ^

@Shaptic I am just converting all fmt.Errorf to errors.New in PR. linter is just very annoying particularly with this rule.

[Shaptic]

@psheth9 ugh, sorry for the extra load. I thought adding my diff suggestions would be linter-fighting-free but I guess not. You can just ignore my suggestions re: that too if you'd like - whatever is easier.

[Shaptic]

Oh yeah also pls add a detailed CHANGELOG entry 🙏 esp. around migration time and storage requirements.