cpu/esp32: add ESP-IDF API

[gschorcht]

Contribution description

This PR is a split-off from PR #17841. It adds the basic structure for an API which is used for ESP-IDF types and functions that are required by RIOT-OS but cannot be included directly due to naming conflicts.

For this purpose, the header files of this API declare the types and functions that are required from the ESP-IDF, but without using the ESP-IDF header files to avoid conflicting names. The implementation of the API then uses the ESP-IDF. In most cases, simple wrapper functions are sufficient.

Testing procedure

Since the basic structure of the API contains almost no functionality, a green CI is sufficient.

Issues/PRs references

Split-off from PR #17841

[benpicco]

Makes it painfully clear why namespaces would sometimes be a good thing to have…

I hope we can enable LTO one day so this at least wouldn't add any run-time cost anymore.

[gschorcht]

@benpicco Can we merge this one? It should then be possible to prepare the PRs for peripherals independent of other PRs once this PR is merged.

[gschorcht]

@benpicco Thanks for reviewing and merging.

[gschorcht]

It should then be possible to prepare the PRs for peripherals independent of other PRs once this PR is merged.

Unfortunately this is not possible after all. The function esp_intr_get_cpu is needed, which is provided by PR #18261. So we have to wait for this PR.