improve error message in SendTransaction json-rpc api (backport #786)

[mergify]

This is an automatic backport of pull request #786 done by Mergify.
Cherry-pick of c8d4d3f has failed:

On branch mergify/bp/release/v0.7.x/pr-786
Your branch is up to date with 'origin/release/v0.7.x'.

You are currently cherry-picking commit c8d4d3f.
  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	modified:   app/ante/ante.go
	modified:   go.sum
	modified:   rpc/ethereum/backend/backend.go
	modified:   rpc/ethereum/namespaces/miner/api.go
	modified:   x/evm/keeper/grpc_query.go
	modified:   x/evm/keeper/msg_server.go
	modified:   x/evm/keeper/utils.go
	modified:   x/evm/types/chain_config.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md
	both modified:   app/ante/eth.go
	both modified:   go.mod
	both modified:   rpc/ethereum/namespaces/eth/api.go
	both modified:   x/evm/keeper/keeper.go
	both modified:   x/evm/keeper/state_transition.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[codecov]

Codecov Report

Merging #789 (c8d4d3f) into release/v0.7.x (39c49c6) will increase coverage by 0.43%.
The diff coverage is 36.25%.

❗ Current head c8d4d3f differs from pull request most recent head 7da009f. Consider uploading reports for the commit 7da009f to get more accurate results

@@                Coverage Diff                 @@
##           release/v0.7.x     #789      +/-   ##
==================================================
+ Coverage           56.87%   57.30%   +0.43%     
==================================================
  Files                  64       71       +7     
  Lines                5352     6041     +689     
==================================================
+ Hits                 3044     3462     +418     
- Misses               2153     2377     +224     
- Partials              155      202      +47     

Impacted Files	Coverage Δ
app/export.go	13.38% <0.00%> (-0.10%)	⬇️
app/test_helpers.go	0.00% <0.00%> (ø)
client/keys.go	0.00% <0.00%> (ø)
client/testnet.go	0.00% <0.00%> (ø)
rpc/ethereum/pubsub/pubsub.go	78.48% <ø> (+78.48%)	⬆️
rpc/ethereum/types/addrlock.go	0.00% <ø> (ø)
rpc/ethereum/types/block.go	50.46% <ø> (+1.37%)	⬆️
rpc/ethereum/types/query_client.go	0.00% <ø> (ø)
rpc/ethereum/types/utils.go	0.00% <0.00%> (ø)
x/evm/client/cli/query.go	0.00% <ø> (ø)
... and 66 more