Always using `_supported_components` causes conflicts when transitive
dependencies also set this variable, e.g., because the developers
followed these code samples.
An even more general approach could be to set
`_${CMAKE_FIND_PACKAGE_NAME}_supported_components` instead, but such a
change should then be applied to other variables for consistency.
Fixes: #23112
This allows the example to also show how to work on systems with
different libdir settings (e.g., Debian multiarch or Red Hat multilib)
rather than a regular `lib` directory.
* Move sections to be same level as Introduction in "Using Dependecies"
* Rename "Importing Exporting Targets" to "Importing Exporting Guide"
* Add an Introduction header to the Tutorial and Importing Exporting Guide
