[Resources.Host] Report amd64 instead of x64 for host.arch

[Kielek]

Fixes #3810

Changes

[Resources.Host] Report amd64 instead of x64 for host.arch

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• [ ] Changes in public API reviewed (if applicable)

[Kielek]

@rjmurillo, FYI

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.04%. Comparing base (4b696ae) to head (e967932).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3811   +/-   ##
=======================================
  Coverage   72.04%   72.04%           
=======================================
  Files         447      447           
  Lines       17834    17834           
=======================================
  Hits        12849    12849           
  Misses       4985     4985           

Flag	Coverage Δ
unittests-Resources.Host	71.85% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/OpenTelemetry.Resources.Host/HostDetector.cs	75.20% <100.00%> (ø)

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