Create "feature flag" for if conditional removal.

[nathanhammond]

Currently in order to improve some of our error messages like in #14554 we pay a double cost in order to leverage runInDebug. In some future state we should be able to use a "feature flag" which allows us to strip things without needing to call it twice and so we can leave the code run in context. That would look something like this:

if (isDebugBuild()) {
  // Do the useful debug thing, probably including try/catch.
} else {
  // Do the performant thing.
}

Do we wish to add a "feature flag" like this? Related though to if (testing) , it is a tremendous way to accidentally troll ourselves.

/cc @krisselden @rwjblue

[locks]

@nathanhammond I wonder if this should go through the RFC process instead?

[nathanhammond]

The thing is we could simply create a new feature flag in a single line of code, this is almost more of a question of "if we want to do it."

[Turbo87]

I think this has been implemented by now, right?

[chancancode]

Yep.