Revert "Use hashed subdir for soong_config modules"

This reverts commit 81b00a8db7.

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

README.md

@@ -594,12 +594,6 @@ modules (`cc_defaults`, `java_defaults`, etc.), which can then be referenced
 by all of the vendor's other modules using the normal namespace and visibility
 rules.
 
-`soongConfigTraceMutator` enables modules affected by soong config variables to
-write outputs into a hashed directory path. It does this by recording accesses
-to soong config variables on each module, and then accumulating records of each
-module's all dependencies. `m soong_config_trace` builds information about
-hashes to `$OUT_DIR/soong/soong_config_trace.json`.
-
 ## Build logic
 
 The build logic is written in Go using the