fix(xsysinfo): include AMD GTT in APU VRAM detection

[leilei3167]

Description

Fixes #12058

On AMD shared-memory APUs (Strix Halo / gfx1151 and similar), rocm-smi --showmeminfo vram only reports the BIOS UMA carve-out (e.g. 512 MiB). Usable HIP memory lives in the much larger GTT pool (often 100+ GiB). LocalAI then showed "512 MB GPU RAM", and auto-fit / MinPerGPUVRAM decisions were sized from that undercount.

This change:

• Queries rocm-smi --showmeminfo all --csv (falls back to vram on older builds)
• Parses VRAM and GTT columns from the CSV header
• When the VRAM/GTT ratio matches a shared-memory APU (GTT >= 8×VRAM), folds GTT into reported Total/Used
• Leaves dedicated dGPU accounting on VRAM only (host GTT aperture is not treated as extra VRAM)

Notes for Reviewers

• Heuristic follows the maint note on GPU RAM detection with incorrect VRAM value #12058: account for usable shared memory without treating all AMD GTT as dedicated VRAM.
• LOCALAI_VRAM_BUDGET remains an allocation cap on the detected total; it still cannot raise a bad detection by itself.

Evidence (old red → new green)

# Before (VRAM-only parse of --showmeminfo all CSV):
go test ./pkg/xsysinfo/ -ginkgo.focus='folds GTT into totals'
# FAIL: Expected <uint64>: 536870912 to equal <uint64>: 133680857088

# After:
go test ./pkg/xsysinfo/ -ginkgo.focus='folds GTT into totals'   # PASS
go test ./pkg/xsysinfo/ -count=1                               # PASS

Signed commits

• Yes, I signed my commits.
• Documentation updated (docs/content/) for user-facing changes, or not applicable