[api] Implement TestGrpcServer_ReadContract by gomock CoreService int…

[LuckyPigeon]

Description

impletment TestGrpcServer_ReadContract in ./api/grpcserver_test.go by gomock CoreService interface

Fixes #3530

Type of change

Please delete options that are not relevant.

• [x] Code refactor or improvement

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] make test
• [x] TestGrpcServer_ReadContract

Test Configuration:

• Firmware version: Ubuntu 21.04
• Hardware:
• Toolchain:
• SDK:

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

[codecov[bot]]

Codecov Report

Merging #3586 (f278118) into master (a20e489) will decrease coverage by 1.52%. The diff coverage is 60.37%.

@@            Coverage Diff             @@
##           master    #3586      +/-   ##
==========================================
- Coverage   75.43%   73.90%   -1.53%     
==========================================
  Files         247      258      +11     
  Lines       22845    23485     +640     
==========================================
+ Hits        17233    17357     +124     
- Misses       4685     5211     +526     
+ Partials      927      917      -10     

Impacted Files	Coverage Δ
action/action_deserializer.go	57.14% <ø> (ø)
action/protocol/poll/nativestaking.go	41.08% <0.00%> (-0.65%)	:arrow_down:
action/protocol/poll/staking_command.go	10.71% <0.00%> (ø)
action/protocol/staking/read_state.go	15.38% <0.00%> (ø)
action/protocol/vote/probationlist.go	87.50% <ø> (ø)
api/blocklistener.go	70.73% <0.00%> (ø)
api/websocket.go	5.17% <0.00%> (-0.19%)	:arrow_down:
blockchain/block/block_deserializer.go	71.15% <ø> (ø)
blockchain/blockchain.go	0.89% <0.00%> (ø)
blockchain/filedao/filedao_legacy.go	85.80% <ø> (ø)
... and 101 more

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