[CODE HEALTH] Fix clang-tidy bugprone-exception-escape warnings in API

[dbarker]

Contributes to #2053

Changes

• replace nostd::get with the noexcept nostd::get_if in API
• Add macros to support try/catch when compiling with and without exceptions
• Add macro for unreachable code paths
• Add unit test coverage for cases with string_view, string_util, and trace/context.
• Fixes the following warnings:

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bugprone-exception-escape (5 warnings)

File	Line	Message
opentelemetry-cpp/api/include/opentelemetry/trace/context.h	26	an exception may be thrown in function 'IsRootSpan' which should not throw exceptions
opentelemetry-cpp/api/include/opentelemetry/trace/trace_state.h	55	an exception may be thrown in function 'FromHeader' which should not throw exceptions
opentelemetry-cpp/api/include/opentelemetry/trace/trace_state.h	118	an exception may be thrown in function 'Get' which should not throw exceptions
opentelemetry-cpp/api/include/opentelemetry/trace/trace_state.h	138	an exception may be thrown in function 'Set' which should not throw exceptions
opentelemetry-cpp/api/include/opentelemetry/trace/trace_state.h	172	an exception may be thrown in function 'Delete' which should not throw exceptions

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cppcoreguidelines-missing-std-forward (1 warnings)

File	Line	Message
opentelemetry-cpp/api/include/opentelemetry/nostd/function_ref.h	81	forwarding reference parameter 'f' is never forwarded inside the function body

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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

❌ Patch coverage is 85.50725% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.05%. Comparing base (8aae05f) to head (0b6d984).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
api/include/opentelemetry/trace/trace_state.h	84.32%	8 Missing ⚠️
api/include/opentelemetry/plugin/detail/utility.h	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3964      +/-   ##
==========================================
- Coverage   90.12%   90.05%   -0.06%     
==========================================
  Files         227      227              
  Lines        7261     7273      +12     
==========================================
+ Hits         6543     6549       +6     
- Misses        718      724       +6     

Files with missing lines	Coverage Δ
...pi/include/opentelemetry/baggage/baggage_context.h	100.00% <100.00%> (ø)
api/include/opentelemetry/common/string_util.h	100.00% <100.00%> (ø)
api/include/opentelemetry/nostd/function_ref.h	77.78% <ø> (ø)
api/include/opentelemetry/nostd/string_view.h	98.15% <ø> (ø)
api/include/opentelemetry/nostd/variant.h	66.67% <ø> (ø)
api/include/opentelemetry/trace/context.h	100.00% <100.00%> (+8.34%)	⬆️
api/include/opentelemetry/trace/tracer.h	100.00% <100.00%> (ø)
api/include/opentelemetry/plugin/detail/utility.h	50.00% <50.00%> (ø)
api/include/opentelemetry/trace/trace_state.h	90.33% <84.32%> (-7.29%)	⬇️

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