Replace Gluecodium cache mechanism with an external solution

[DanielKamkha]

Currently Gluecodium provides a built-in caching mechanism for generated files. The only use case where this mechanism is needed is preserving time stamps when files are re-generated in place, so that CMake could properly recognize these files as "not changed" if the file contents are the same.

This mechanism is hard to test, prone to corner-case errors, and is very unsafe in concurrency scenarios (both inside a single Gluecodium run and with several parallel Gluecodium instances). The proposal is to replace this mechanism with something external to Gluecodium itself. It can be, for example, a part of the CMake tool-chain as it is only needed for CMake usages anyway.