Refactor Api::Environment

[imtayadeway]

Took some suggestions out of #14624 and bundled them with some other refactorings. The result is a little longer, but I think it adds clarity and consistency.

Among the changes:

1. Got rid of an unnecessary begin block
2. Implement the normalized_attrs data using sets instead of hashes (we don't use the values, we just assign all values to true
3. Remove the normalized_attrs hash altogether, which should lower the memory footprint of this module, since it duplicated some other data which never got GC'd
4. Provide a more consistent API for checking if an attribute needs to be normalized with some top-level Api.<type>_attribute? helper methods

@Fryguy thanks for some of these suggestions!
@miq-bot add-label api, refactoring
@miq-bot assign @abellotti

[abellotti]

@imtayadeway can you run a performance test with before (hash) and after (set), of GET 1000 VM's with expand=resources. Thanks.

[miq-bot]

This pull request is not mergeable. Please rebase and repush.

[Fryguy]

😍 I love it!

[miq-bot]

Checked commits imtayadeway/manageiq@3742b42~...f1a3b03 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
3 files checked, 0 offenses detected
Everything looks fine. 🍰

[imtayadeway]

@abellotti OK I have some numbers for you! Couldn't quite get to 1000 but I had 714 Vms in my database so I limited to 700 in my query. I ran the query 20x on each run (after warming up) so hopefully any big quirks will have been somewhat evened out:

Here's before:

tim@tim-thinkpad:~/src/manageiq$ time for i in `seq 1 20`; do curl --user admin:smartvm 'localhost:3000/api/vms?expand=resources&limit=700' &> /dev/null; done

real	8m51.058s
user	0m0.084s
sys	0m0.028s

And after:

tim@tim-thinkpad:~/src/manageiq$ time for i in `seq 1 20`; do curl --user admin:smartvm 'localhost:3000/api/vms?expand=resources&limit=700' &> /dev/null; done

real	8m47.522s
user	0m0.068s
sys	0m0.052s

So the data says: slightly faster ;) Pinch of salt though, I wouldn't want to seriously make that claim - there are many extraneous things that could account for that. Importantly though, I think we can say it's in the same ball park. LMK if I can do anything else!

[abellotti]

This is fine @imtayadeway same ballpark, less in user more in system. Thanks for running the tests 🎵

[abellotti]

LGTM !! 👍