[ETW Exporter] Add Virtual destructor for TailSampler, Update Maintainer mode warnings for MSVC

[lalitb]

Fixes #1896

Changes

• Add default virtual destructor for etw::TailSampler.
• Enforce the missing virtual destructor warning as error for MSVC while building in maintainer mode.
• The inclusion of <future> header with this warning enforced fails with below error, so suppressed the warning for this header:
  C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.34.31933\include\pplwin.h(80,1): error C5204: 'Concurrency::details::_DefaultPPLTaskScheduler': class has virtual functions, but its trivial destructor is not virtual; instances of objects derived from this class may not be destructed correctly [D:\a\opentelemetry-cpp\opentelemetry-cpp\build\sdk\src\metrics\opentelemetry_metrics.vcxproj]
• VS2019 v16.x reports signed/unsigned mismatch errors at few places while building in maintainer mode, fixed those errors.

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 #1897 (c3d2921) into main (a343da0) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1897   +/-   ##
=======================================
  Coverage   85.74%   85.74%           
=======================================
  Files         171      171           
  Lines        5243     5243           
=======================================
  Hits         4495     4495           
  Misses        748      748           

Impacted Files	Coverage Δ
...lemetry/ext/http/client/curl/http_operation_curl.h	100.00% <ø> (ø)
...metrics/export/periodic_exporting_metric_reader.cc	73.92% <ø> (ø)

[lalitb]

This is ready for review now.

[marcalff]

LGTM, thanks for the fix (and for using the maintainer mode)