Convert some properties to Configurable properties

Focusing on the properties needed to remove soong config modules from
packages/modules/Virtualization.

- prebuilt_etc's src and srcs
- filegroup's srcs and exclude_srcs
- rust's cfgs

Bug: 342006386
Test: m nothing --no-skip-soong-tests
Change-Id: I6971da744a17955f98104948e6f9614776955782