This relands aosp/2470068. The original CL was submitted as part of a
stack that broke tm and udc. Those branches still contain soong modules
with min_sdk_version of type (kind+level).
Test: m nothing on tm and udc (via go/abtd)
Bug: 208456999
Change-Id: I8e013ec10530372f70f0ab0505b7eebeee2b360b
InvalidApiLevel:
This will be used for error handling if a user provided api level is
not recognized
PrivateApiLevel:
This will be used to differentiate the api level of sdk_version:"" from
sdk_version:"current" or sdk_version:"<active_codename>" (all used to be
FutureApiLevel previously). This was not necessary previously since the
type of min_sdk_version was SdkSpec(kind+level). Since it had access to
kind, it could check that it was not SdkSpecPrivate
Test: m nothing
Change-Id: I628b443c34bf2ec258d947dfec09f38b126bc6bb
