add support for intersection & union in search operations

[dsa0x]

Summary

This PR addresses this enhancement issue #849, which suggested adding support for intersection and union search. The PR adds support for and and or operators.

• and operation returns a union of values in each list (i.e no duplicates)
• or returns a list of all values, not minding duplicates.

Release Note

new: support for intersection and union search through the use of and and or operators.

Documentation

[codecov-commenter]

Codecov Report

Merging #968 (f642f5e) into main (5019f3e) will decrease coverage by 7.22%.
The diff coverage is 76.47%.

@@            Coverage Diff             @@
##             main     #968      +/-   ##
==========================================
- Coverage   48.15%   40.93%   -7.23%     
==========================================
  Files          61       69       +8     
  Lines        5401     6491    +1090     
==========================================
+ Hits         2601     2657      +56     
- Misses       2520     3551    +1031     
- Partials      280      283       +3     

Impacted Files	Coverage Δ
cmd/rekor-cli/app/search.go	20.58% <50.00%> (+0.89%)	⬆️
pkg/api/index.go	41.44% <76.66%> (ø)
cmd/rekor-cli/app/pflags.go	85.71% <100.00%> (+0.38%)	⬆️
pkg/sharding/ranges.go	46.01% <0.00%> (-1.26%)	⬇️
pkg/types/alpine/v0.0.1/entry.go	54.77% <0.00%> (-1.25%)	⬇️
pkg/api/api.go	0.00% <0.00%> (ø)
pkg/api/public_key.go	0.00% <0.00%> (ø)
pkg/api/trillian_client.go	0.00% <0.00%> (ø)
pkg/api/entries.go	0.00% <0.00%> (ø)
... and 4 more

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[dlorenc]

Oh wow, this is really cool!

[asraa]

Thanks! Quick question on correctness/expectation here.

[asraa]

This looks amazing now! Great work. Good job on the unit tests and testing in e2e.
The implementation was very cool to read.