Remove uses of lodash/isRegExp

[zertosh]

Continuing the gradual reduction in lodash use. This is not exactly like lodash's implementation. In Node it defers to util.isRegExp, which is cross-realm safe. In Browsers it does a Object.prototype.toString.call(value) === '[object RegExp]'. I'm fine with switching to the toString approach.

Q	A
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Deprecations?
Spec Compliancy?
Tests Added/Pass?
Fixed Tickets
License	MIT
Doc PR
Dependency Changes	X

[mention-bot]

@zertosh, thanks for your PR! By analyzing the history of the files in this pull request, we identified @forivall, @hzoo and @boopathi to be potential reviewers.

[loganfsmyth]

I'm curious, is there a specific goal in mind? I was for the others because I usually prefer natives if it is easy, but this case is less obvious because of the realm issues, and manually writing toString is kind of gross.

[zertosh]

I think all of lo-dash can actually be removed (only clone and merge are tricky)- saving a non-trivial amount of load time.

[codecov-io]

Current coverage is 89.22% (diff: 100%)

Merging #5180 into master will increase coverage by <.01%

@@             master      #5180   diff @@
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  Files           203        203          
  Lines          9835       9839     +4   
  Methods        1071       1073     +2   
  Messages          0          0          
  Branches       2620       2620          
==========================================
+ Hits           8775       8779     +4   
  Misses         1060       1060          
  Partials          0          0          

Powered by Codecov. Last update d76092b...485a522

[xtuc]

Underscore uses:

// Is the given value a regular expression?
  _.isRegExp = function(obj) {
    return !!(obj && obj.test && obj.exec && (obj.ignoreCase || obj.ignoreCase === false));
  };

I think checking for test and exec is safer but could match with other objects.

[zertosh]

After thinking about it some more, I think the toString (although ugly), is the most effective and honest. Since it's only in 2 places, I don't think it's worth dwelling on the esthetics. Thoughts?

[xtuc]

If think if we use a function there, we could use the lodash function.

[zertosh]

I'll leave this change for last. It'll be clearer that keeping _.isRegExp makes no sense when it's the last lodash function used.