Remove soong.config, FileConfigurableOptions, MegaDevice config.

No current use cases for soong.config and user-editable local
configuration options for Soong, so let's remove it to reduce the API
surface.

The MegaDevice configuration is used for building every module, for
every cpu variant, for every architecture, but it apparently isn't
used for a while now.

Test: m nothing
Test: TH
Fixes: 174188200
Change-Id: I2550e70ff6f9c8b57e9a7cc517d6a119a032a27a
diff --git a/cmd/soong_build/main.go b/cmd/soong_build/main.go
index b88803a..d758de2 100644
--- a/cmd/soong_build/main.go
+++ b/cmd/soong_build/main.go
@@ -79,7 +79,7 @@
 	srcDir := filepath.Dir(flag.Arg(0))
 	var ctx *android.Context
 	configuration := newConfig(srcDir)
-	extraNinjaDeps := []string{configuration.ConfigFileName, configuration.ProductVariablesFileName}
+	extraNinjaDeps := []string{configuration.ProductVariablesFileName}
 
 	// Read the SOONG_DELVE again through configuration so that there is a dependency on the environment variable
 	// and soong_build will rerun when it is set for the first time.