Improve bound and cache update checks

[2opremio]

No description provided.

[Shaptic]

Something is up with event request validation, I think

[Shaptic]

Looks like there's a test failing so pls fix that first but otherwise this LGTM:

    get_events_test.go:436: 
        	Error Trace:	/home/runner/work/stellar-rpc/stellar-rpc/cmd/stellar-rpc/internal/methods/get_events_test.go:436
        	Error:      	Error message not equal:
        	            	expected: "startLedger must be positive"
        	            	actual  : "startLedger must be positive and <= than endLedger"
        	Test:       	TestGetEventsRequestValid