[GN]: support for loadable modules

+ Adds a new target type loadable_module and tool type solink_module. loadable_module will trigger the solink_module tool type in the toolchain.
+ Updates reference.md and editor configs.

BUG=369774

Review URL: https://codereview.chromium.org/1386783003

Cr-Original-Commit-Position: refs/heads/master@{#354077}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 027840da082368b8d51f06b9c310807540e50eea
27 files changed
tree: 202e790b41edd5a48fd51141d1318af5608951ba
  1. tools/