Revert "Use hashed subdir for soong_config modules"

This reverts commit 81b00a8d.

Reason for revert:
* select() will supersede Soong config modules.
* A tiny change can make hundreds of gigabytes rebuilt.
* Hashed out/ directories are not cleaned.
* Even without this trace, AB build time is fast enough, thanks to
  product-specific ninja files and so on.

Bug: 348548855
Test: m --no-skip-soong-tests
Change-Id: If9a97df1e161a9ef0fb1b801f9e129b71b11d1ac