Native serialization for MutableVamana index

[razdoburdin]

This PR introduce native serialization for MutableVamana index.

Main changes are:

1. New overload of svs::index::vamana::auto_dynamic_assemble required for direct deserialization accepts lazy loaders and call them in a flexible order to cover legacy serialized models.
2. The test file tests/svs/index/vamana/dynamic_index.cpp is returned to the test build, as far as it is the right place for serialization tests.
3. Some minor refactoring to streamline the logic.