implement locate and updatedb

[Qelxiros]

closes #60

Given that locate has largely been replaced by (m|p)locate, I was unable to find a version of locate packaged for my system (latest Arch Linux), and the packaged version of updatedb does not use the LOCATE02 db format. When running updatedb from source, I encountered errors that were not immediately fixable. As such, this implementation is largely untested, but it's better to have something here to be improved upon.

[sylvestre]

cool, thanks :)
a bunch of tasks are failing

[sylvestre]

add please add tests :)

[codecov]

Codecov Report

Attention: Patch coverage is 86.50794% with 85 lines in your changes missing coverage. Please review.

Project coverage is 87.30%. Comparing base (a607612) to head (cb3e399).

Files with missing lines	Patch %	Lines
src/locate/mod.rs	83.13%	49 Missing and 21 partials ⚠️
src/updatedb/mod.rs	92.75%	11 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #536      +/-   ##
==========================================
- Coverage   87.69%   87.30%   -0.40%     
==========================================
  Files          31       35       +4     
  Lines        6893     6930      +37     
  Branches      324      353      +29     
==========================================
+ Hits         6045     6050       +5     
- Misses        617      628      +11     
- Partials      231      252      +21     

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[Qelxiros]

A couple notes:

• User flags are ignored for updatedb. GNU/BSD/Apple implementations all use a shell script, so they have direct access to su. I'm not sure if there's a better solution from rust, but I left it alone for now.
• Performance is pretty significantly worse than GNU for updatedb. It might be a problem with find, since updatedb delegates most of the work to it. Locate is about on par with GNU for the one test that I did. I'd love another set of eyes to look for improvements.
• I'll fix coverage issues tomorrow.
• Looks like Release / plan is failing due to the Ubuntu 20.04 test runner no longer being available. Is that as simple a fix as updating it to 22.04 or later?

[sylvestre]

Suggested change

// Copyright 2017 Google Inc.