Implement global default non-recording span

[MrAlias]

This adds a non-recording span implementation to the internal global package and returns that span implementation by default. This implementation, like the non-recording span implementation in the trace package, performs no operation except to return the parent SpanContext of the span. This ensures traces are not broken if no SDK is registered.

This copies the nonRecordingSpan implementation rather than importing it from a centralized package to avoid a dependency cycle. It may be possible through a large refactor to unify this, but that can be done in the future if there is ever deemed a sufficient need.

Resolves #1893
Resolves #877

[codecov]

Codecov Report

Merging #1901 (464d950) into main (b6d5442) will decrease coverage by 0.0%.
The diff coverage is 50.0%.

@@           Coverage Diff           @@
##            main   #1901     +/-   ##
=======================================
- Coverage   79.4%   79.3%   -0.1%     
=======================================
  Files        139     139             
  Lines       7414    7425     +11     
=======================================
+ Hits        5889    5892      +3     
- Misses      1279    1286      +7     
- Partials     246     247      +1     

Impacted Files	Coverage Δ
internal/global/trace.go	83.7% <50.0%> (-16.3%)	⬇️
trace/noop.go	46.1% <0.0%> (-7.7%)	⬇️
sdk/trace/batch_span_processor.go	85.6% <0.0%> (-1.6%)	⬇️
trace.go	100.0% <0.0%> (+33.3%)	⬆️