fix: use InstrumentationLibrary in metrics.

[TommyCpp]

Currently we don't use InstrumentationLibrary to store the instrumentation library information. This should help unify things a little bit. My only concern is whether there will be any cases that users cannot use static string as argument(need to fetch intrumentation information somewhere else). So far I haven't thought any, so leave it as it is for now.

[codecov]

Codecov Report

Merging #393 (4f4066d) into master (47b54ee) will increase coverage by 0.00%.
The diff coverage is 52.77%.

@@           Coverage Diff           @@
##           master     #393   +/-   ##
=======================================
  Coverage   49.31%   49.31%           
=======================================
  Files          66       66           
  Lines        5368     5376    +8     
=======================================
+ Hits         2647     2651    +4     
- Misses       2721     2725    +4     

Impacted Files	Coverage Δ
opentelemetry/src/api/metrics/observer.rs	0.00% <ø> (ø)
opentelemetry/src/api/metrics/registry.rs	0.00% <0.00%> (ø)
opentelemetry/src/api/metrics/config.rs	20.68% <11.11%> (-1.90%)	⬇️
opentelemetry/src/api/metrics/descriptor.rs	33.33% <60.00%> (+3.10%)	⬆️
opentelemetry/src/api/metrics/meter.rs	50.00% <66.66%> (-2.64%)	⬇️
opentelemetry/src/global/metrics.rs	83.33% <71.42%> (-16.67%)	⬇️
opentelemetry/src/api/metrics/noop.rs	20.00% <100.00%> (ø)
...ntelemetry/src/sdk/metrics/aggregators/ddsketch.rs	76.95% <100.00%> (+0.19%)	⬆️

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[jtescher]

Yeah I think requiring the static lifetime is fine here

[TommyCpp]

Yeah I think requiring the static lifetime is fine here

👍 We can also switch to the owned string if someone brings a valid use case and that shouldn't break existing APIs.