add pending pool tx query RPC and address blacklist

[LeoGuo621]

• 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.

• [ ] Wrote tests

• [ ] Updated relevant documentation (docs/)

• [ ] Added a relevant changelog entry to the Unreleased section in CHANGELOG.md

• [ ] Reviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge PR #XYZ: [title]" (coding standards)

[codecov-commenter]

Codecov Report

Merging #3186 (dcfcc44) into dev (0274e47) will increase coverage by 0.00%. The diff coverage is 33.33%.

:exclamation: Current head dcfcc44 differs from pull request most recent head c07b8b5. Consider uploading reports for the commit c07b8b5 to get more accurate results

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@@           Coverage Diff           @@
##              dev    #3186   +/-   ##
=======================================
  Coverage   36.55%   36.55%           
=======================================
  Files         443      443           
  Lines       46486    46495    +9     
=======================================
+ Hits        16991    16996    +5     
- Misses      28229    28234    +5     
+ Partials     1266     1265    -1     

Impacted Files	Coverage Δ
app/config/config.go	26.72% <33.33%> (+0.09%)	:arrow_up:

... and 1 file with indirect coverage changes