Adding flavors and build types fallback logic

using the project app module variants as the base for creating all bazel build targets of all modules.

fallback logics come to play when a dependency doesn't have a flavor or buildType or both that exist in the app module, in that case, fallbacks are used to select a substitute variant from existing variants in the dependency

for example in the following build graph
app -> B -> C

app - with flavors[f1,f2] buildTypes[ debug, release ]
B - android Lib buildTypes [ debug , release ]
C - kotlin / java lib

for module B bazel targets will be created for B according to the app module

bf1Debug // which is equal to original debug variants in B
bf2Debug // which is equal to original debug variants in B
bf1Release // which is equal to original Release variants in B
bf2Release // which is equal to original Release variants in B

the reason for this is to create the dependency graph in bazel for all app module variants.