Remove zpages

[reyang]

Remove the ZPages component:

• The total download number is very low (9.4k in the past 3+ years) https://www.nuget.org/packages/OpenTelemetry.Exporter.ZPages.
• There hasn't been any real change for years https://github.com/open-telemetry/opentelemetry-dotnet/commits/main/src/OpenTelemetry.Exporter.ZPages.
• There is no plan to make this official from the specification perspective.

[codecov]

Codecov Report

Merging #4604 (c13bf29) into main (4712c3a) will decrease coverage by 0.06%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4604      +/-   ##
==========================================
- Coverage   85.25%   85.20%   -0.06%     
==========================================
  Files         320      312       -8     
  Lines       12753    12532     -221     
==========================================
- Hits        10873    10678     -195     
+ Misses       1880     1854      -26     

see 5 files with indirect coverage changes

[CodeBlanch]

LGTM

[Kielek]

AutoInstrumentation is not using this package.

Please remember to deprecate it also on nuget.org side (worth to make a bit bigger cleanup open-telemetry/opentelemetry-dotnet-contrib#1100).

[cijothomas]

There is no plan to make this official from the specification perspective.

https://github.com/open-telemetry/opentelemetry-specification/blob/main/experimental/trace/zpages.md
Would this doc be updated to indicate so?

[cijothomas]

Agree with this.
Maintainers may either keep a readme.md page with this info or update the nuget package to indicate its deprecaed.