[blockindex] move config.Indexer to blockindex package

[huof6829]

Description

move config.Indexer to blockindex package

Fixes #3505

Type of change

Please delete options that are not relevant.

• [] Bug fix (non-breaking change which fixes an issue)
• [] New feature (non-breaking change which adds functionality)
• [] Code refactor or improvement
• [] Breaking change (fix or feature that would cause a new or changed behavior of existing functionality)
• [] This change requires a documentation update

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

• [] make test
• [] fullsync
• [] Other test (please specify)

Test Configuration:

• Firmware version:
• Hardware:
• Toolchain:
• SDK:

Checklist:

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

[codecov]

Codecov Report

Merging #3573 (784585f) into master (a20e489) will decrease coverage by 1.34%.
The diff coverage is 54.46%.

@@            Coverage Diff             @@
##           master    #3573      +/-   ##
==========================================
- Coverage   75.43%   74.08%   -1.35%     
==========================================
  Files         247      254       +7     
  Lines       22845    23380     +535     
==========================================
+ Hits        17233    17321      +88     
- Misses       4685     5134     +449     
+ Partials      927      925       -2     

Impacted Files	Coverage Δ
action/protocol/staking/read_state.go	15.38% <0.00%> (ø)
api/grpcserver.go	79.49% <ø> (+0.55%)	⬆️
blockchain/blockchain.go	0.89% <0.00%> (ø)
blockchain/filedao/filedao_legacy.go	85.80% <ø> (ø)
blockchain/filedao/filedao_v2.go	98.51% <ø> (ø)
blockchain/pubsubmanager.go	0.00% <0.00%> (ø)
config/config.go	94.06% <ø> (+9.31%)	⬆️
consensus/scheme/rolldpos/rolldposctx.go	73.47% <0.00%> (-0.18%)	⬇️
db/db_bolt.go	72.51% <ø> (-0.19%)	⬇️
db/kvstore_impl.go	61.64% <ø> (ø)
... and 67 more

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