Select statements are a new blueprint feature inspired by bazel's select
statements. They are essentially alternative syntax for soong config
variables that require less boilerplate. In addition, they support
making decisions based on a module's variant, which will eliminate
the need for manual property struct manipulation, such as the arch
mutator's arch: and target: properties.
In order to support decisions based on the variant, select statements
cannot be evaluated as soon as they're parsed. Instead, they must be
stored in the property struct unevaluated. This means that individual
properties need to change their type from say, string, to
Configurable[string]. Currently, only configurable strings, bools, and
string slices are supported, but more types can be added later.
The module implementation must call my_property.Evaluate(ctx) in order
to get the final, resolved value of the select statement.
Bug: 323382414
Test: go tests
Change-Id: I62f8721d7f0ac3d1df4a06d7eaa260a5aa7fcba3
6437d4e737