[REMOVAL] Remove ZPAGES

[marcalff]

Follow up on:

• https://github.com/open-telemetry/opentelemetry-cpp/pull/2291

Removal date tentative, pending discussion on deprecation pr.

Upon removal, close the following issues:

• 2271

• 184

• 166

Upon removal, file an issue on the specifications to remove C++ from the zpage spec (and possibly remove the zpage spec entirely)

[2023-12-08] Filed in the spec as:

• https://github.com/open-telemetry/opentelemetry-specification/issues/3786

[github-actions[bot]]

This issue was marked as stale due to lack of activity.

[esigo]

to be removed after 1.13 release

[marcalff]

Actually, deprecation was done in release 1.12.0, so removal in 1.13.0 is ok.

Removal to occur after 1.13.0 is:

• 2383