Resolves: #109803

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

• Projection primary keys were accounted only through projection-specific metrics and system.projection_parts, while the aggregate primary key metrics and parent system.parts fields did not include them.
• This change makes TotalPrimaryKeyBytesInMemory, TotalPrimaryKeyBytesInMemoryAllocated, system.parts.primary_key_size, system.parts.primary_key_bytes_in_memory, system.parts.primary_key_bytes_in_memory_allocated, and the corresponding system.parts_columns memory fields include primary keys from projections stored inside the parent part. Projection-specific metrics and system.projection_parts remain available for inspecting projection-only usage.
• system.tables does not currently expose primary-key-memory fields, so there is no matching system.tables column to update. Existing system.tables row, part, and byte counters keep their current semantics.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)