add some unit tests for estimateGas

[yihuang]

Description

• add unit tests for estimateGas
• add some test environment setup, Closes Setup more sophisticated testing environment in unit test suite #323
• add a precompiled erc20 smart contract in the test case, instruction to compile is included in the comment

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #324 (29364cd) into main (e61594e) will increase coverage by 5.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #324      +/-   ##
==========================================
+ Coverage   47.38%   52.42%   +5.04%     
==========================================
  Files          46       46              
  Lines        4611     4614       +3     
==========================================
+ Hits         2185     2419     +234     
+ Misses       2348     2093     -255     
- Partials       78      102      +24     

Impacted Files	Coverage Δ
x/evm/keeper/grpc_query.go	70.64% <100.00%> (+14.16%)	⬆️
x/evm/keeper/keeper.go	64.63% <0.00%> (+4.26%)	⬆️
x/evm/keeper/abci.go	26.66% <0.00%> (+26.66%)	⬆️
x/evm/keeper/state_transition.go	62.50% <0.00%> (+57.58%)	⬆️
x/evm/keeper/msg_server.go	69.69% <0.00%> (+69.69%)	⬆️

[yihuang]

One of the test cases currently fail for estimated gas number different from the one returned by geth.

[fedekunze]

ACK, one minor suggestion

[yihuang]

One of the test cases currently fail for estimated gas number different from the one returned by geth.

the test case failure is due to unclean context, now added capability for test suite to commit and begin a new block.

[fedekunze]

the test case failure is due to unclean context, now added capability for test suite to commit and begin a new block.

can you fix the failing test? Then we can merge this PR

[yihuang]

the test case failure is due to unclean context, now added capability for test suite to commit and begin a new block.

can you fix the failing test? Then we can merge this PR

that one is already fixed, current failure seems caused by something else, I'm checking it now.

[yihuang]

the test case failure is due to unclean context, now added capability for test suite to commit and begin a new block.

can you fix the failing test? Then we can merge this PR

fixed now, remove the commit in test suite setup.