Add simple tool for processing status availability files

[travisbrown]

The twcc check-existence tool takes as input a list of tweet IDs on standard input and outputs a CSV file like this, where 0 indicates that the tweet is unavailable (either deleted or from a suspended or locked account) and 1 indicates that it's live:

9142291,1
10643701,1
18984851,1
34661512,1
48826972,1
72706082,1
75507232,1
102425362,0
119141862,1
120506682,0

We've published this output for large batches of tweet IDs at s3://twitter-metadata/status-availability/. The output there includes rechecks, where we check the same IDs multiple times (to get a fresh view after months, etc.).

It can be useful to combine these results into a single list that indicates the most recently known status for each tweet ID, which is what this tool does. You point it to a directory of CSV files like the example above, where the filenames correspond to chronological order, and it outputs a sorted list of each unique tweet ID and its most recent status.

Note that it takes about four minutes to run on our current availability files (representing a hundred-million-ish tweets and retweets, most of which have been checked at least twice).

[codecov-commenter]

Codecov Report

Merging #41 (7012473) into main (5afe23f) will decrease coverage by 0.19%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
- Coverage   26.63%   26.44%   -0.20%     
==========================================
  Files          44       45       +1     
  Lines        2775     2795      +20     
==========================================
  Hits          739      739              
- Misses       2036     2056      +20     

Impacted Files	Coverage Δ
src/bin/availability.rs	0.00% <0.00%> (ø)

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