[RESOURCE DETECTOR] Add the host resource detector

[mateenali66]

Fixes #4413

Changes

Adds the host resource detector in resource_detectors/, setting host.name, host.arch and host.id per semantic conventions, with Linux, MacOS and Windows support.

Platform specifics, also documented on the class:

• host.name: gethostname() on Linux/MacOS, GetComputerNameExW() on Windows
• host.id: /etc/machine-id with /var/lib/dbus/machine-id fallback on Linux, gethostuuid() on MacOS, the HKLM\SOFTWARE\Microsoft\Cryptography\MachineGuid registry value on Windows. Omitted when no source is available (for example Linux containers without a machine id).
• host.arch: mapped at compile time from predefined architecture macros to the semconv values, omitted for architectures the conventions do not enumerate.

Follows the process detector layout (detector + detail/ utils split for testability). Verified by running the utils on MacOS arm64 (hostname, arm64, hardware UUID all populated); Linux and Windows paths exercised in CI.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

❌ Patch coverage is 80.43478% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.58%. Comparing base (2499c49) to head (f4d3c12).

Files with missing lines	Patch %	Lines
resource_detectors/src/host_detector.cc	71.43%	6 Missing ⚠️
resource_detectors/src/host_detector_utils.cc	88.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4418      +/-   ##
==========================================
- Coverage   82.59%   82.58%   -0.01%     
==========================================
  Files         509      511       +2     
  Lines       19972    20018      +46     
==========================================
+ Hits        16494    16529      +35     
- Misses       3478     3489      +11     

Files with missing lines	Coverage Δ
resource_detectors/src/host_detector_utils.cc	88.00% <88.00%> (ø)
resource_detectors/src/host_detector.cc	71.43% <71.43%> (ø)

... and 1 file with indirect coverage changes

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[dbarker]

Looks good. Thank you! Just requesting addition of this detector to the install test.

[marcalff]

LGTM, thanks for the feature.