fix(rpc): handle case when node is not persisting abci responses

[GAtom22]

Description

When setting the configuration parameter discard_abci_responses = true, all JSON-RPC methods that rely on TendermintBlockResult (e.g.: eth_gasPrice, eth_getBlockByNumber, eth_getBlockByHash, eth_getTransactionByHash, eth_getTransactionReceipt, eth_getTransactionLogs, eth_feeHistory) will not return the expected result (usually null) and in some cases cause a panic.

For example, in eth_gasPrice the error logs are:

4:48PM INF Served eth_gasPrice conn=10.100.1.9:40160 duration=594.644458 err="method handler crashed" module=geth reqid=2231
4:48PM ERR RPC method eth_gasPrice crashed: runtime error: invalid memory address or nil pointer dereference
goroutine 109462359 [running]:
github.com/ethereum/go-ethereum/rpc.(*callback).call.func1()
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/service.go:200 +0x85
panic({0x2c07660?, 0x59fa270?})
	/usr/local/go/src/runtime/panic.go:914 +0x21f
github.com/evmos/evmos/v14/rpc/backend.(*Backend).GasPrice(0x1?)
	/go/src/github.com/evmos/evmos/rpc/backend/call_tx.go:391 +0x2e
github.com/evmos/evmos/v14/rpc/namespaces/ethereum/eth.(*PublicAPI).GasPrice(0xc1a7ac8120)
	/go/src/github.com/evmos/evmos/rpc/namespaces/ethereum/eth/api.go:304 +0x4d
reflect.Value.call({0xc0128ec7d0?, 0xc01e1108c8?, 0x7efc27a56370?}, {0x308f76e, 0x4}, {0xc4ea675410, 0x1, 0x0?})
	/usr/local/go/src/reflect/value.go:596 +0xce7
reflect.Value.Call({0xc0128ec7d0?, 0xc01e1108c8?, 0x0?}, {0xc4ea675410?, 0xc06c69acb0?, 0x53e005?})
	/usr/local/go/src/reflect/value.go:380 +0xb9
github.com/ethereum/go-ethereum/rpc.(*callback).call(0xc014c7da40, {0x3fbc150?, 0xc4d9003b80}, {0xc4aeabec80, 0xc}, {0x5d82240, 0x0, 0x4f54cf?})
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/service.go:206 +0x37c
github.com/ethereum/go-ethereum/rpc.(*handler).runMethod(0xc4aeabec90?, {0x3fbc150?, 0xc4d9003b80?}, 0xc4da7ad030, 0x0?, {0x5d82240?, 0x2dd3700?, 0xc06c69ae08?})
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/handler.go:388 +0x3c
github.com/ethereum/go-ethereum/rpc.(*handler).handleCall(0xc4daf22240, 0xc4ea6753b0, 0xc4da7ad030)
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/handler.go:336 +0x22f
github.com/ethereum/go-ethereum/rpc.(*handler).handleCallMsg(0xc4daf22240, 0x30?, 0xc4da7ad030)
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/handler.go:297 +0xbd
github.com/ethereum/go-ethereum/rpc.(*handler).handleMsg.func1(0xc4ea6753b0)
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/handler.go:138 +0x2f
github.com/ethereum/go-ethereum/rpc.(*handler).startCallProc.func1()
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/handler.go:225 +0xbe
created by github.com/ethereum/go-ethereum/rpc.(*handler).startCallProc in goroutine 109099080
	/go/pkg/mod/github.com/evmos/go-ethereum@v1.10.26-evmos-rc2/rpc/handler.go:221 +0x79
 module=geth
4:48PM INF Served eth_gasPrice conn=10.100.1.8:47380 duration=600.599497 err="method handler crashed" module=geth reqid=2232
4:48PM INF Served eth_getLogs conn=10.100.1.8:43508 duration=497.484693 err="failed to fetch header by number (latest): block result not found for height 16461313" module=geth reqid=2

This PR adds the corresponding changes to handle this gracefully and avoid the panic.
As a result, the user will get the following response:

{"jsonrpc":"2.0","id":73,"error":{"code":-32000,"message":"block result not found for height 22. node is not persisting abci responses"}}

---

Closes #XXX

[codecov]

Codecov Report

Merging #1863 (0b75e81) into main (576e2c2) will decrease coverage by 0.02%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             main    #1863      +/-   ##
==========================================
- Coverage   70.53%   70.52%   -0.02%     
==========================================
  Files         315      315              
  Lines       23404    23412       +8     
==========================================
+ Hits        16509    16511       +2     
- Misses       6079     6084       +5     
- Partials      816      817       +1     

Files	Coverage Δ
rpc/backend/backend.go	76.47% <ø> (ø)
rpc/backend/blocks.go	84.92% <100.00%> (ø)
rpc/backend/chain_info.go	81.28% <100.00%> (-0.11%)	⬇️
rpc/backend/call_tx.go	59.41% <57.14%> (-0.33%)	⬇️
rpc/backend/utils.go	43.09% <40.00%> (-0.41%)	⬇️

[Vvaradinov]

https://github.com/Mergifyio backport release/v15.0.x

[mergify]

backport release/v15.0.x

✅ Backports have been created

• #1868 fix(rpc): handle case when node is not persisting abci responses (backport #1863) has been created for branch release/v15.0.x but encountered conflicts