Moves to specifying attributes as a map, such at it is possible to add
additional attributes conditionally. This is in particular useful once
supporting the `enabled` property which will add
`target_compatible_with`
Test: go test soong tests
Change-Id: Iade8eed1ce3acb1d1712a9ee3119d9ae59675624
Have binary and library bp2build convert `libs` to
`deps` for bazel
Bug: 196083751
Test: python_{binary,library}_conversion_test.go
Test: build/bazel/ci/mixed_{libc,droid}.sh
Change-Id: I2d5f6ef2e83dd608910edb7adb2eb9a56d25293c