fix: commented out importer test (fixes #659)

[tomtau]

Closes: #659

Description

updated the importer test as a test suite
plus added the block export file
from https://github.com/cosmos/ethermint/blob/development/importer/blockchain

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For contributor use:

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• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
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[fedekunze]

Nice! can we also re-add the CI check?

[fedekunze]

ACK, pending CI fix

[codecov]

Codecov Report

Merging #691 (30b680d) into main (ac75a9a) will decrease coverage by 0.18%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #691      +/-   ##
==========================================
- Coverage   57.38%   57.20%   -0.19%     
==========================================
  Files          64       63       -1     
  Lines        5583     5545      -38     
==========================================
- Hits         3204     3172      -32     
+ Misses       2215     2209       -6     
  Partials      164      164              

Impacted Files	Coverage Δ
tests/importer/chain_ctx.go

[fedekunze]

@tomtau it seems that the importer test was also run on the rpc-tests and that's why they are failing, can you fix it?

https://github.com/tharsis/ethermint/runs/3974441400?check_suite_focus=true

[tomtau]

#700