Flavors support

[mohamadk]

supporting variants (Flavor+buildTypes) in Grazel

With this PR grazel will create all bazel targets for all available build variants(including unit tests) in the application.

It supports flavored configurations like:

flavor1Implementation project(path: ':sample-library-flavor1')
testImplementation ....
etc...

targets are created in BUILD.bazel file with the following naming convention
"target-name-flavor1-debug"
for example
sample-android-flavor1-debug

Resources are also managed based on the variant and will be added to their respective bazel targets.

resource_files = glob([
        "src/main/res/**",
    ]) + custom_res(
        dir_name = "res-debug",
        resource_files = glob([
            "src/main/res-debug/values/strings.xml",
        ]),
        target = "sample-android-flavor1-debug",
    ) + GOOGLE_SERVICES_XML,

Internal project dependencies are managed based on

1. The type of the project (android library or kotlin/java Library)
2. availability of the requested flavor in the dependent module
   for example in the following graph
   A (with flavor [googleplay, hwi] ) -> B
   if B is an android project it should have the respective flavors or at least the same build types, otherwise, the bazel target cannot be linked, and migration will fail. (if B is a java/Kotlin library it will be added as a dependency simply)

Known Issues:

• At the moment load macros are unnecessarily repeated

• external dependencies with flavor support with the usage of maven classifier is not supported yet
  implementation "com.grab:library-name:version:classifier"