Include block-generator and validator as algorand-indexer subcommands.

[winder]

Summary

Move remaining test utilities to algorand-indexer. Group them in a visible "util" subcommand.

Test Plan

Ran through the different commands manually.

[codecov-commenter]

Codecov Report

Merging #891 (52d8cb3) into develop (2aad7db) will increase coverage by 0.08%.
The diff coverage is 95.65%.

@@             Coverage Diff             @@
##           develop     #891      +/-   ##
===========================================
+ Coverage    58.60%   58.69%   +0.08%     
===========================================
  Files           38       39       +1     
  Lines         4559     4581      +22     
===========================================
+ Hits          2672     2689      +17     
- Misses        1557     1561       +4     
- Partials       330      331       +1     

Impacted Files	Coverage Δ
cmd/block-generator/generator/daemon.go	64.28% <80.00%> (ø)
cmd/algorand-indexer/main.go	33.94% <100.00%> (+5.23%)	⬆️

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