Remove previously deprecated code

[bartgol]

Motivation

Some c++17 utilities were backported in ekat, to allow using them with C++14. They were deprecated a while ago, and eamxx stopped using them. Now that we bumped the major version is a good time to say bye bye.

Since we're dropping some deprecated interfaces, update the minor version too.

Closes #357

[Copilot]

Pull request overview

This PR removes previously deprecated C++14 backports of C++17 utilities from EKAT’s core, along with the associated unit test, and updates build metadata accordingly.

Changes:

• Delete deprecated backport headers (ekat_std_any.hpp, ekat_std_enable_shared_from_this.hpp) and stop installing them.
• Remove the std_meta unit test and its CMake registration.
• Bump EKAT minor version from 2.0.0 to 2.1.0.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/core/std_meta.cpp	Removes the unit test that exercised the deprecated ekat::any implementation.
tests/core/CMakeLists.txt	Stops building/running the removed std_meta test.
src/core/ekat_std_enable_shared_from_this.hpp	Deletes deprecated ekat::enable_shared_from_this backport header.
src/core/ekat_std_any.hpp	Deletes deprecated ekat::any backport header.
src/core/ekat_parameter_list.hpp	Updates docs to reference std::any rather than ekat::any.
src/core/CMakeLists.txt	Removes deleted headers from the installed/public header set.
CMakeLists.txt	Updates EKAT version metadata (minor bump).

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