Add a "base" to sgx_enclave_configuration
Add a "base" to sgx_enclave_configuration

This allows users to derive configurations based on non-default
configuration values that are stored in other configuration targets.
This feature uses Bazel's providers feature to track config values at
compilation time.

PiperOrigin-RevId: 264909949
Change-Id: I6ca5732b99ce48de518da59dd5328105aee033a9

google/asylo,google/asylo,google/asylo,google/asylo,google/asylo,google/asylo