chore: move span method for context in trace API #40

[vmarchaud]

• I moved both [sg]etSpan/[sg]etSpanContext utils into the trace API
• I also moved [sg]etBaggage to the baggage folder (next to createBaggage)
  • As discussed in the SIG, we should think about the place for baggage utils, i think it makes more sense in the propagation API

Fixes #40

[codecov]

Codecov Report

Merging #47 (8e3b8da) into main (e938882) will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   94.65%   94.72%   +0.07%     
==========================================
  Files          39       40       +1     
  Lines         505      512       +7     
  Branches       80       80              
==========================================
+ Hits          478      485       +7     
  Misses         27       27              

Impacted Files	Coverage Δ
src/context/context.ts	82.35% <ø> (-10.15%)	⬇️
src/api/trace.ts	96.55% <100.00%> (+0.71%)	⬆️
src/baggage/index.ts	100.00% <100.00%> (ø)
src/trace/NoopTracer.ts	95.45% <100.00%> (ø)
src/trace/context-utils.ts	100.00% <100.00%> (ø)

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[Flarna]

As this is a breaking change an entry in upgrade guideline (introduced in #43) should be added

[obecny]

lgtm

[dyladan]

Once conflicts are resolved this can merge