Create EffectiveVersion* functions for ApiLevel

These functions already exist on SdkSpec(kind+level) and are used for
computing the effective version for vendor modules compiling against
current or system_current which depends on the sdkKind

Create these functions for ApiLevel to support migrating MinSdkVersion
from SdkSpec to ApiLevel. Since the "api level" of vendor modules depend
on the sdk_kind as well, these functions will continue to exist on
SdkSpec.

Test: m nothing
Test: no diff in ninja files (this should be a no-op)
Bug: 208456999

Change-Id: Iee5a936e72b02b4fab9e457082d46fb8358eff16