Kimwitu++, a tool for processing trees

Kimwitu++ is the successor to Kimwitu. Like Kimwitu, it is a tool for
processing trees (i.e. terms). It is a meta tool: Kimwitu++ can be used
for generating software - especially when building compilers. Kimwitu++
has its own input language, which allows the definition for the tree
structure and of functions operating on the tree. It uses the input to
generate a number of C++ files, which are then bound to a program using
the C++ compiler.

Closes #22470.

Signed-off-by: Xiyue Deng <manphiz@gmail.com>