Optimize dependency resolution code path and introduce experiment to limit parallelism

[arunkumar9t2]

Various improvements to optimize the dependency resolution process which remains on the critical path:

• Ensure dependency resolution for unselected variants are skipped, only variants that pass the variant filter configured by the user will go through resolution as part of the migration.
• Ensure Variant's extendsFrom property are correctly set for Android tests and unit test variants
• Introduce an experiments extension property that adds limitDependencyResolutionParallelism flag which can be used to limit the no of parallel dependency resolution happening by establishing inter task dependencies that mirror the project graph. This basically ensure successors in a graph are resolved first before trying to resolve the predecessor nodes.
• Updated tests.