Schema related files are moved there. This excludes schema files that
also interact with mutations, because the mutation module depends on
the schema. Those files will have to go into a separate module.
Closes#12858
The Lua sstable consumer loads a script from the specified path then
feeds the mutation fragment stream to the script via the
sstable_consumer methods, each method of which the script is allowed to
define, effectively overloading the virtual method in Lua.
This allows for very wide and flexible customization opportunities for
what to extract from sstables and how to process and present them,
without the need to recompile the scylla-sstable tool.
