Merge changes Ie883eb45,If46a2f74,I8f4c5395,Ic4eb169d,I2b2408ef, ... into rvc-dev

* changes:
  Replace references to droiddoc with droidstubs
  Allow walkPayloadDeps visitor to control walk flow
  Add apex_available to sysprop_library
  Improve missing apex_available message
  Split TestApexAvailable into separate tests
  Use reflect.Zero(type) to get value to clear field
  Sdk snapshot set compile_multilib per OsType
  Remove old SdkMemberType API for creating snapshot modules
  Improve consistency of handling java snapshot properties
  Make new module creation API more flexible
  Add abstraction for tracking compile multilib usages
  Add support for using cc_library in sdk/module_exports
  Extract the osTypeSpecificInfo code from module creation loop
  Extract archTypeSpecificInfo code from module creation loop
  Clean up the main module creation loop
  Add support for cc_prebuilt_library
  Refactor prebuilt to use srcs supplier function
  Output properties before sets in snapshot module
  Remove SdkMemberType.FinalizeModule
  Follow up a review comment that was missed
  Copy shared_libs and system_shared_libs to module snapshot
  Support extracting common values from embedded structures
  Refactor common value extraction
  Copy white listed apex available settings into snapshot
  Disable installation for sdk snapshot versioned prebuilts
  Remove special handling of test_ apexes
  Remove special handling of com.android.art.debug/release
  Allow sdk members to vary by os type
  Add support for multiple os types
  Copy sdk_version to cc library snapshots
  Refactor java_library/java_test snapshot processing
  Refactor snapshot module creation
  Enable androidmk processing in sdk testing
  Add a nice install paths for module SDKs and exports.
  Copy apex_available properties to snapshot modules
  Improve documentation of CompileMultiTargets and related properties
  Only check copy rules into the snapshot directory
  Simplify java library sdk member code
  Add CommonOS variant for sdk
  Fix bug in error reporting when adding duplicate properties
  Avoid invoking sdk member to add empty list of dependencies
  Add windows to the list of available OS's in sdk tests
  Add support for cc_library_headers in sdk/module_exports
  Prune any empty property sets from the modules before transforming
  Simplify cc library sdk snapshot handling of include dirs/headers
  Add support for transforming a property set after its contents
  Fix issues with bp transformation