Add schema_url support to both Resource and InstrumentationLibrary

[ThomsonTan]

Fixes #948

Changes

Add schema_url as an optional parameter to both API and SDK.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #979 (8578ab8) into main (0500d6d) will increase coverage by 0.03%.
The diff coverage is 96.67%.

@@            Coverage Diff             @@
##             main     #979      +/-   ##
==========================================
+ Coverage   95.38%   95.41%   +0.03%     
==========================================
  Files         161      161              
  Lines        6817     6833      +16     
==========================================
+ Hits         6502     6519      +17     
+ Misses        315      314       -1     

Impacted Files	Coverage Δ
api/include/opentelemetry/trace/noop.h	86.21% <0.00%> (ø)
api/include/opentelemetry/trace/tracer_provider.h	100.00% <ø> (ø)
api/test/trace/provider_test.cc	80.00% <ø> (ø)
sdk/include/opentelemetry/sdk/resource/resource.h	100.00% <ø> (ø)
...k/instrumentationlibrary/instrumentation_library.h	100.00% <100.00%> (ø)
sdk/src/resource/resource.cc	96.67% <100.00%> (+4.67%)	⬆️
sdk/src/trace/tracer_provider.cc	74.36% <100.00%> (+0.68%)	⬆️
sdk/test/resource/resource_test.cc	93.86% <100.00%> (+0.41%)	⬆️
sdk/test/trace/tracer_provider_test.cc	100.00% <100.00%> (ø)

[lalitb]

LGTM. Thanks for adding the support :)