[Bindings][Compiler] Add Bazel support for Python bindings (#24980)

IREE's compiler Python support is available through CMake, but its
generated dialect bindings, native extensions and compiler tool wrappers
are not exposed as Bazel targets. Downstream projects using Bazel
therefore need to maintain their own build definitions to package Python
bindings that match the compiler they build.

Providing these targets upstream lets consumers build Python compiler
packages against their chosen IREE revision and keeps the binding
definitions alongside the sources they describe. The bindings use
`IREECompiler`'s shared C API so Python code can inspect and construct
IR, then invoke the compiler using the same MLIR implementation.
Consumers retain control of package and wheel assembly.

Assisted-By: GPT-6-Astra