This reverts commit abc3a698abc0dfea19040007a7c57d04c3bb6865.

Unfortunately it caused various problems:

- Minimum cmake version for extra-cmake-modules does not contain the
  required module
- Even with newer cmake it had issue with old policy that was not fixed
  until very late that breaks packages using old policy

CCMAIL: kde-frameworks-devel@kde.org

Finding Qt6 tools without also finding any library component only works
in the COMPONENT form, see also MR !233.

Fixes issue #7

If linker does not support the linker flag, do not enable it, on alpine
e.g. musl does not support the ASAN, if it is enabled unconditionally,
it will cause the linker to error out

This is apparently needed for static QML plugins to work properly.

When the major version of a module is >1, Qt expects a .MajorVersion
suffix on the module path. Since we are already doing this for the
shared library install path, extract that code to a shared macro and
reuse it for the prefix path in the generated qrc.

To avoid ambiguity with ECMQmlModule.cmake.

To preserve backward compatibility, we keep a version around of
ECMQMLModules.cmake that warns a user of it being moved and includes the
new file.

This contains some helper functions to make it easier to create QML
modules through CMake. It takes care of several things that currently
need to be done manually.

It adds four tests for the four primary ways that it can be used,
either as shared/static library and with or without C++ plugin.

Semantically this is an ECM module, because it can be used to manage deprecated
Qt API and from any project which use ecm_generate_export_headers