Add a section to the `define_property()` documentation which
details the behavior when attempting to redefine an existing
property. (The command is silently ignored.)
Provide an example using `get_property()` to examine a property
definition created with `define_property()`.
Remove the requirement that the variable name have a prefix while
keeping the suffix requirement. Require that the property name
contains an underscore. Update docs and tests accordingly.
Fixes: #23340
The BRIEF_DOCS and FULL_DOCS are remnants from before the
Sphinx-based documentation when CMake's internal structures
for defining properties included fields for their documentation.
They are no longer mandatory for define_property() and haven't
been in practical use for some time. The main use of the command
has evolved to now be more about how to initialize and inherit
properties, so update the docs to reflect that change in focus.
Issue: #20698
INITIALIZE_FROM_VARIABLE is new in CMake 3.23, but the
versionadded note was missing in the original commit. The docs
also failed to mention that the new option only applies to target
properties.
Amends fce24e4f10 (define_property(): Add INITIALIZE_FROM_VARIABLE
argument, 2022-01-13)
