In a following patch, all DevTools moz.build files will use DevToolsModules to
install JS modules at a path that corresponds directly to their source tree
location. Here we rewrite all require and import calls to match the new
location that these files are installed to.
We also provide an opt-out for the original behavior, and use it in various
consumers that look like they need fixing up. Most of the usage here is in
code with persistence considerations, where we may need some sort of migration
path.
