Extend list of permitted classes for YAML safe load and allow aliases

[nmburgan]

When trying to load hosts_preserved.yml, all of these classes need to be able to be loaded. We should probably serialize fewer things to this file, but in the meantime, this allows things to work. This also uses strings for the list, since not all the classes are loaded and available at the time we are declaring this array. This also allows aliases, since we are using those in the hosts_preserved.yml file.

[codecov]

Codecov Report

Base: 74.93% // Head: 74.93% // No change to project coverage 👍

Coverage data is based on head (1b4bfbd) compared to base (f60ac94).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 1b4bfbd differs from pull request most recent head 4335485. Consider uploading reports for the commit 4335485 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1758   +/-   ##
=======================================
  Coverage   74.93%   74.93%           
=======================================
  Files          82       82           
  Lines        4876     4876           
=======================================
  Hits         3654     3654           
  Misses       1222     1222           

Impacted Files	Coverage Δ
lib/beaker/options/hosts_file_parser.rb	95.45% <100.00%> (ø)

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[donoghuc]

I think this is a good thing to get released. If someone can eventually look in to paring down what we persist for known hosts in the first place that would also be good.

[ekohl]

Is there some test that exercises the code that requires the serialization? As you can see, we already had tests for 3.1 but since they passed, clearly there's a gap in coverage.

[nmburgan]

Good call. I added a hosts_preserved.yml to try to load in the spec. It's not testing the specific permitted classes or anything, just verifying it can load the file. We can get fancier with it if you think it's important.