Blender Git Loki

LibOverride: Do not store some heavy data from override IDs.

This commit removes geometry from meshes and shapekeys, and embedded
files, from liboverride IDs.

This data is never overrideable, there is no reason to store extra
useless copies of it in production files.

See T78944.

Note that we may add more data to be skipped on write for liboverrides
in the future, but this commit should address all the most important
cases already.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D9810