Split out providers into "standalone" python packages

### Body As part of making it possible to move out of providers from Airflow core repository (we have not decided yet on it, we just want to make it possible) we should turn Airflow Providers into "real" packages. Currently those packages are build "dynamically" -> https://github.com/apache/airflow/blob/main/dev/provider_packages/prepare_provider_packages.py is used as part of `breeze release-management prepare-provider-packages` to extract parts of the "airflow/providers/<provider>" sources dynamically, generate setup.* and pyproject.toml files dynamically and build the providers from those dynamically generated temporary folders. This has some disadvantages - for example it does not make reproducible builds possible, and it requires complex `breeze` command, CI image and the python script in the image to build the packages (CI image is used to make sure all dependencies are installed and to provide isolation and cleanup between builds, also it allows to isolate (security) the host from container building the packages whenbuilding the providers in case of builds from contributor forks). But this got us through last 3 years of releasing airflow and providers separately :). With recent changes (#32604 upcoming #32048, the upcoming #33907 and a number of other changes already implemented in the past - we are quite close to make it possible to split out providers to "standalone" packages - where each provider is a separate "compliant with standard" package and has a complete independent directory where you can build the package without moving the sources around, using standard python tooling. This would require everything that relates to the providers to move to those directories (docs, tests are notably shared between airflow and providers in "docs" and "tests" and they should be moved around). We should also eventually add automation of checking if there is anything left in core that refers to providers #11435. The early draft POC attempts to add scripts to automate…