Problem: rpc stream overhead even if not used

[yihuang]

Solution:

• init the underlying subscriptions lazily.

Closes: #XXX

Description

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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

Attention: Patch coverage is 0% with 23 lines in your changes missing coverage. Please review.

Project coverage is 46.17%. Comparing base (885530b) to head (7e3a2b7).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
rpc/stream/rpc.go	0.00%	22 Missing ⚠️
server/json_rpc.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #551   +/-   ##
========================================
  Coverage    46.16%   46.17%           
========================================
  Files          181      181           
  Lines        18125    18124    -1     
========================================
  Hits          8368     8368           
+ Misses        9040     9039    -1     
  Partials       717      717           

Files with missing lines	Coverage Δ
server/json_rpc.go	0.00% <0.00%> (ø)
rpc/stream/rpc.go	0.00% <0.00%> (ø)

[mmsqe]

do we need skip PendingTxListener as well?

[yihuang]

do we need skip PendingTxListener as well?

good catch, let's ignore pending tx listener here, it's feed by check-tx ante handler, which don't block state machine.

the overhead of the other subscriptions are in the block commit flow.