Rename config_toml.py to config.py

This file now does more than just configure the rustc TOML file so the
name is being changed to reflect this.

Test: do_build.py
Change-Id: I75daff96dde63fb3ace4f78312cb403b43558ad9

Author: chriswailes

config_toml.py renamed to config.py

@@ -25,7 +25,7 @@
 import sys
 
 import build_platform
-import config_toml
+import config
 from paths import *
 
 
@@ -127,7 +127,7 @@ def main():
     # Cargo.lock
     #
 
-    config_toml.configure()
+    config.configure()
 
     # Trigger bootstrap to trigger vendoring
     #