Magic *_keys and *_values Remap functions

[binarylogic]

Yes, I said "magic" 🐰 . #5377, #5784, and #5783 introduce functions that walk and mutate the entire event. They are simple solutions that avoid hard-to-follow traversal/walk constructs in Remap, like the ones being discussed in #4518. These functions are much easier to implement, read, and understand. To avoid the repetitive nature of defining functions that end with _keys and _values it would be nice to get these functions automatically. I'm on the fence with this but wanted to record an explicit decision here before we move forward with the blocked issues.

Requirements

• Automatically define *_keys and *_values for functions that operate on single values (accept a single value as their first parameter).

[binarylogic]

@JeanMertz I'd like to get your approval/opinion on this before starting on #5377, #5784, and #5783. I'm not opposed to not doing this and just creating the referenced functions like any other function.

[JeanMertz]

Closing this as we are going to work on iteration this quarter, which should solve this need as well.