msgpack-cxx: add version 7.0.0

[toge]

Summary

Changes to recipe: msgpack-cxx/7.0.0

Motivation

There is a breaking change in 7.0.0.

Details

msgpack/msgpack-c@cpp-6.1.1...cpp-7.0.0

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• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[conan-center-bot]

Conan v1 pipeline ✔️

Warning

Conan Center will stop receiving updates for Conan 1.x packages soon - please see announcement.

All green in build 1 (4d5a8444d0704320df5c59001e42ddcd3ba9b93e):

• msgpack-cxx/7.0.0:
  Built 5 packages out of 11 (All logs)

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Conan v2 pipeline ✔️

Note: Conan v2 builds are now mandatory. Please read our discussion about it.

All green in build 1 (4d5a8444d0704320df5c59001e42ddcd3ba9b93e):

• msgpack-cxx/7.0.0:
  Built 4 packages out of 5 (All logs)

[ericLemanissier]

@franramirez688 @jcar87 previous CI used to test the recipe on all supported platforms, cf https://c3i.jfrog.io/c3i/misc-v2/summary.html?json=https://c3i.jfrog.io/c3i/misc-v2/logs/pr/25568/6/msgpack-cxx/6.1.1//summary.json even if there was a single Package ID.
It looks like the new CI does not run more test than valid package ID in https://github.com/conan-io/conan-center-index/pull/25812/checks
Does it mean that header only recipes will never be evaluated in Windows and MacOs context ?