Reduce dependency on futures crate

[robjtede]

Size of dep graph:

	before	after
opentelemetry	47	38
opentelemetry-contrib	122	113
opentelemetry-datadog	136	130
opentelemetry-http	53	44
opentelemetry-jaeger	129	120
opentelemetry-otlp	140	139
opentelemetry-prometheus	52	43
opentelemetry-aws	137	128
opentelemetry-semantic-conventions	48	39
opentelemetry-stackdriver	180	180
opentelemetry-zipkin	218	211
opentelemetry-zpages	149	149

Only opentelemetry-otlp could not have it's futures dep removed (yet). It is blocked on the release of tikv/grpc-rs#554 in order for the codegen to reference std's Future.

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Rob Ede (363e2ce)

[djc]

Nice, would be happy to merge this.

[djc]

How do you measure size of individual crate's dep graphs?

[robjtede]

It's not scientific but: cargo tree -e=normal -p="$p" | wc -l.

I don't know any incantation to just get a flat, dupe-less list of deps in the graph.

[robjtede]

Updated with slightly more scientific: cargo tree -e=normal --prefix=none -p="$p" | grep -v '*' | wc -l | xargs

[codecov]

Codecov Report

Merging #684 (00d2666) into main (50510e3) will not change coverage.
The diff coverage is 85.71%.

@@           Coverage Diff           @@
##             main     #684   +/-   ##
=======================================
  Coverage   63.81%   63.81%           
=======================================
  Files          96       96           
  Lines        7725     7725           
=======================================
  Hits         4930     4930           
  Misses       2795     2795           

Impacted Files	Coverage Δ
opentelemetry/src/runtime.rs	69.76% <ø> (ø)
opentelemetry/src/sdk/export/metrics/stdout.rs	0.00% <ø> (ø)
opentelemetry/src/sdk/metrics/controllers/push.rs	0.00% <0.00%> (ø)
opentelemetry/src/sdk/trace/runtime.rs	56.00% <ø> (ø)
opentelemetry/src/trace/context.rs	46.42% <ø> (ø)
opentelemetry/src/trace/mod.rs	72.88% <ø> (ø)
opentelemetry-jaeger/src/exporter/mod.rs	58.72% <100.00%> (ø)
opentelemetry/src/sdk/trace/span_processor.rs	82.01% <100.00%> (ø)

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