Frontend utility functions should be exported as ES modules and not pollute global space

Currently we have dozens of utility functions like gl.utils.backOff(), gl.utils.rstrip(), and gl.utils.prettyTime.parseSeconds(). These are all imported in main.bundle.js on EVERY page load and put into globally accessible variables.

This has several downsides:

1. all utility functions are loaded on all pages
2. we needlessly pollute the global space
3. these utility modules are "impure modules" since they have side effects and this prevents several optimizations that webpack can make when bundling them
4. since we don't explicitly import functions where they are needed, it is difficult to truly visualize our dependency tree. every module that uses these
5. our linter cannot detect when these methods are invalid

To make this transition easy, I recommend we take a two-step approach.

1. Transform all util functions into proper ES module exports, but continue to export them as globals as well, wrapped in a method that will spit out a deprecation warning when in DEVELOPMENT or TEST environments (production compilation will remove these warnings as dead code, so there is no performance tradeoff).

2. Slowly convert all utility function calls into proper import statements, gradually removing the global exports one at a time as they are no longer needed.