chore(host-metrics): do not diag.warn if using default options

[trentm]

Currently 'new HostMetrics();' will diag.warn 'No meter provider, using default'.
This shouldn't be a warning. It is fine to use the default meter provider.

/cc @legendecas as code owner

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.55%. Comparing base (e0fa929) to head (2728051).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2767      +/-   ##
==========================================
- Coverage   90.60%   90.55%   -0.06%     
==========================================
  Files         168      168              
  Lines        8078     8076       -2     
  Branches     1548     1547       -1     
==========================================
- Hits         7319     7313       -6     
- Misses        759      763       +4     

Files with missing lines	Coverage Δ
...ages/opentelemetry-host-metrics/src/BaseMetrics.ts	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

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