Call to_a on cached ObjectSpace enumerator

[warhammerkid]

Based on the existence of the @@requested_contants code path, it seems safe for this method to return an Array in some cases, so simply caching the array of all Modules rather than the enumerator should be safe. Also, I have included the recommended optimization to derive all_classes from all_modules, which both simplifies things (no need for the @@requested_constants code path in both methods), as well as improves performance by skipping a full ObjectSpace traversal again.

Motivation

Closes #1974

Tests

This is simply an optimization to an existing tested behavior.

[warhammerkid]

I have signed the CLA!

[amomchilov]

Thanks for your contribution! I have 2 small suggestions, but otherwise LGTM!

Once you ship this, I'll do a quick benchmark against our monolith. I'm expecting there should be pretty substantial gains!

[amomchilov]

I know it's kind of niche, but .grep(Class) is noticeably faster (last I benchmarked it), since it calls Class#=== directly, without needing the overhead of a block call like select needs

Suggested change

	all_modules.select { |k| k.is_a?(Class) },
	all_modules.grep(Class),

[egiurleo]

I actually didn't know this! Good to know.

[amomchilov]

Good to know.

It's cursed knowledge, as Aaron would say

[amomchilov]

2 other nice benefits:

1. It removes the need for this cast because Enumerable#grep has a special overload for metatypes.
2. The k.is_a?(Class) was calling is_a? on k, which could be arbitrary user code that breaks things. Class === k would always be on a receiver we control, Class.

[paracycle]

Yes, @amomchilov is spot on, especially around the use of ===. In this project, we prefer to use === over is_a? whenever it is possible, since the receiver of === is usually under our control, so the result can be more dependable.

[amomchilov]

May as well change this too, to be consistent.

Suggested change

	@@requested_constants.select { |k| k.is_a?(Module) }
	@@requested_constants.grep(Module)

[amomchilov]

Tested on our monolith, works great. We'll merge once we sort our CI issues

[egiurleo]

Rebased to get CI fixes!