[MRG] update lca summarize output to output total counts

[ctb]

This PR adds a total_counts column to the CSV output of sourmash lca summarize per #1833.

Addresses most of #1833.

[codecov]

Codecov Report

Merging #1838 (ff6fe8e) into latest (13bf0d5) will increase coverage by 8.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           latest    #1838      +/-   ##
==========================================
+ Coverage   81.92%   89.94%   +8.02%     
==========================================
  Files         118       88      -30     
  Lines       12783     8592    -4191     
  Branches     1705     1705              
==========================================
- Hits        10472     7728    -2744     
+ Misses       2047      600    -1447     
  Partials      264      264              

Flag	Coverage Δ
python	89.94% <100.00%> (ø)
rust	?

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Impacted Files	Coverage Δ
src/sourmash/lca/command_summarize.py	87.82% <100.00%> (ø)
src/core/src/errors.rs
src/core/src/ffi/mod.rs
src/core/src/from.rs
src/core/src/ffi/nodegraph.rs
src/core/src/ffi/index/revindex.rs
src/core/tests/storage.rs
src/core/src/index/mod.rs
src/core/src/index/sbt/mhbt.rs
src/core/src/ffi/utils.rs
... and 21 more

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[ctb]

Ready for review and merge @sourmash-bio/devs

[mr-eyes]

In the test case output, the counts column equals to the total_counts I am not sure if this test case validates the total_count when it's different than the count.

[ctb]

In the test case output, the counts column equals to the total_counts I am not sure if this test case validates the total_count when it's different than the count.

thanks @mr-eyes - added a new test!

[mr-eyes]

Looks great! Thank you.

[ctb]

thank you!