Fix read_mclust returning zero units for .t files

[h-mayorquin]

Two bugs in MClustSortingExtractor made read_mclust silently return a sorting with zero units for plain .t files (reported in #4602). First, the extension search relied on the truthiness of Path.glob(...), which returns a generator and is therefore always truthy, so the format was always detected as t64 regardless of which files were present; materializing the glob with sorted(...) makes the check reflect what is actually on disk. Second, MClust 3.x writes big-endian uint64 timestamps into the plain .t suffix while the reader assigns uint32 to any non-64 extension, so each 64-bit value was read as two 32-bit words; dropping the zero high words (only for the t family read as uint32) recovers the timestamps, matching the community reference loader.

Closes #4602.

[alejoe91]

Thasnk @h-mayorquin !!!