Unify handling of disabled/enabled features

Currently (depending on feature) enabling/disabling is done by either compile time #ifdef, returning BLE_HS_ENOTSUP in runtime for disabled features, or by wrapping one feature on top of other API.

Runtime errors are not the best IMHO as those should be reserved for recoverable scenarios. I propose that we always do #ifdef so that application developer can detect mis-configuration at build time.

The issue names no files, tests, or entry points. Begin by inventorying how features are currently enabled or disabled, then define the scope needed for all features to use compile-time #ifdef handling; done means misconfiguration is detected at build time rather than through runtime BLE_HS_ENOTSUP errors.

Written by the indexing model from the issue text.