Rework cflags system and make objects be specified per-version

[TheNathannator]

• The cflag system now allows inheriting from another set of cflags. Inheritance is evaluated bottom-up, starting with includes first.
• I reorganized cflags to more easily allow lib-specific optimization flags as needed, and added in a bunch of flag sets for libraries in the project.
• Objects are now specified per-version, since not all objects are compiled the same way on all versions.
• Both the flag and object versioning files now have schemas, for documentation and editor validation support.
• I disabled the Missing configuration for <...> logging since all it does for us now is just spam the console when reconfiguring.
• I added another VS Code task for ninja diff, and made the ninja task the default build task, since that makes more sense than just building the current file.

[TheNathannator]

Before I forget:

One caveat of the new cflags/object system is that Ninja will not auto-config on changes anymore, a manual re-config is needed. I'm not sure how to get Ninja to check flags.json/objects.json for changes and reconfigure accordingly.

[TheNathannator]

Got that figured out and fixed, it now once again auto-configures on modification.