fix: adapt to new libnvme Python API (Phase 2 + exception hierarchy)

[martin-belanger]

Update nvme-stas to match the libnvme Python binding changes from nvme-cli PR #3332 (redesign) and the subsequent exception hierarchy refactor:

• nvme.global_ctx() → nvme.GlobalCtx()
• nvme.host() → nvme.Host()
• nvme.ctrl() → nvme.Ctrl()
• host.dhchap_key → host.dhchap_host_key
• ctrl.connected() → ctrl.connected (property, not method)
• ctrl.supported_log_pages → ctrl.get_supported_log_pages
  (raises NvmeError on failure instead of returning None)

The try/except (TypeError, IndexError) guard around the dlp_supp_opts extraction is removed: get_supported_log_pages() always returns a fixed-size list of integers or raises, so neither exception is structurally possible any more.

Update the TestDc.Ctrl stub in test-controller.py to expose connected as a @property instead of a method, matching the new API.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 60.84%. Comparing base (d561432) to head (96168ee).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
staslib/ctrl.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #488      +/-   ##
==========================================
+ Coverage   60.77%   60.84%   +0.06%     
==========================================
  Files          16       16              
  Lines        2616     2613       -3     
==========================================
  Hits         1590     1590              
+ Misses       1026     1023       -3     

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