Add a new image and distro definition for using on the WebKit CI for WPE perf bots

[clopez]

• This adds a new image named core-image-webkit-dev-ci-tools-tests which will be used on the WebKit CI for building an image containing everything needed to build WebKit and run tests (perf-tests, layout-tests, etc). The image itself doesn't contain WebKit (WPE).

• It adds also a python-is-python3 recipe that creates a symlink to provide the unversioned python interpreter as python3.

For more info see: https://bugs.webkit.org/show_bug.cgi?id=249604

Note: this patch is also on the WebKit PR at https://github.com/WebKit/WebKit/pull/7885 (file: Tools/yocto/rpi/fix-nativesdk-image-defs.patch) The idea is to update that WebKit PR (or do a new PR if that one lands before this) with the reduced delta.

[clopez]

This image definition is also used to build a cross-toolchain and SDK with:

bitbake core-image-webkit-dev-ci-tools-tests -c populate_sdk

[clopez]

I'm uploading a new version of the patch that I think address the previous comments and also tunes a bit further how the image is generated to also include -dev packages and so it becomes possible to actually build WebKit on the target device (native build) if wished.

[clopez]

Committed it to main on 46fbfbc58f82abc3dc8794c630172d4554be0830 I added the GDB TUI suggestion and also a few other packageconfig options that were previously set on the targets local.conf (in the WebKit patch) but makes more sense to have those options here in the distro definition