Fix by-name endpoints reporting TotalRecordCount=0 next to a populated Items array

`GetItemValues` -- the shared path behind `/Artists`, `/AlbumArtists`, `/Genres`,
`/MusicGenres` and `/Studios` -- disabled the total record count whenever the
query carried no `Limit`:

    if (!filter.Limit.HasValue)
    {
        filter.EnableTotalRecordCount = false;
    }

A request without an explicit limit therefore came back with N entries in `Items`
and `TotalRecordCount = 0`. Clients that page on the reported total -- the
documented contract every other list endpoint honours -- read that as an empty
library. `/Items` and `/Persons` do not share this path and report the count
correctly, which is what makes the inconsistency visible from the outside.

Measured against master with a 62-track music library:

    GET /Artists?UserId=...              -> TotalRecordCount=0  Items=5
    GET /Artists?UserId=...&limit=100    -> TotalRecordCount=5  Items=5

Dropping the block costs nothing: `representativeIds` is materialised into a
`List<Guid>` a few lines below regardless, so `.Count` was already available and
the count is now reported from it. Callers that genuinely want to skip the count
still can -- `EnableTotalRecordCount = false` is honoured as before.

The block also mutated the caller's own query object, so a query instance reused
across calls silently lost its total after the first limitless one. That is
covered by a test as well.

0 files changed, 0 insertions, 0 deletions