Add support for writing all Soong config variables into @soong_injection.

Also remove the need to use bp2build_available on
soong_config_module_types as we want to convert every single of them
into the tree for a complete soong_injection soong_config_variables.bzl
file.

The variables are split into their bool, value and string types
respectively, as they all need to be handled differently on the Bazel
product_platform side, as well as for generating constraint values and
settings. For example, value variables need to integrate with
TemplateVariableInfo, and string variables need to include the string
value itself into the select key/constraint value.

Sample soong_config_variables.bzl file: https://gist.github.com/jin/cef700bfb20c8656a931306dd71d47e1

Test: CI
Bug: 198556411
Change-Id: I8665dd1269a507edb37de62407ed3641564bea5c
diff --git a/android/bazel.go b/android/bazel.go
index f4686a0..9efc033 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -15,7 +15,6 @@
 package android
 
 import (
-	"android/soong/bazel"
 	"fmt"
 	"io/ioutil"
 	"path/filepath"
@@ -25,11 +24,28 @@
 	"github.com/google/blueprint/proptools"
 )
 
+type bazelModuleProperties struct {
+	// The label of the Bazel target replacing this Soong module. When run in conversion mode, this
+	// will import the handcrafted build target into the autogenerated file. Note: this may result in
+	// a conflict due to duplicate targets if bp2build_available is also set.
+	Label *string
+
+	// If true, bp2build will generate the converted Bazel target for this module. Note: this may
+	// cause a conflict due to the duplicate targets if label is also set.
+	//
+	// This is a bool pointer to support tristates: true, false, not set.
+	//
+	// To opt-in a module, set bazel_module: { bp2build_available: true }
+	// To opt-out a module, set bazel_module: { bp2build_available: false }
+	// To defer the default setting for the directory, do not set the value.
+	Bp2build_available *bool
+}
+
 // Properties contains common module properties for Bazel migration purposes.
 type properties struct {
 	// In USE_BAZEL_ANALYSIS=1 mode, this represents the Bazel target replacing
 	// this Soong module.
-	Bazel_module bazel.BazelModuleProperties
+	Bazel_module bazelModuleProperties
 }
 
 // namespacedVariableProperties is a map from a string representing a Soong