Remove memberDepsMutator, SdkAware et al

Previously, the memberDepsMutator was responsible for tracking the
membership of modules in an sdk/module_exports (or corresponding
snapshot). That was only used to determine whether a module was in a
versioned sdk snapshot so that it could be treated differently by the
build. As there are no versioned sdk snapshots these can now be
removed.

This change removes the memberDepsMutator, along with SdkAware and
related types that are no longer used.

Bug: 260237150
Test: m nothing
Change-Id: I2668679a42d5b3f33f9e06d5b59804dfdae5f6da