QML Script Compiler should provide insights into what's compiled

Users generally would like to know whether the script compiler makes their code faster, and whether it's worth the longer compile times. That can't be answered without actual benchmarking. We can however provide some insights into what the Script Compiler is actually doing:

• Which/How many bindings and functions can actually get compiled?
• How much time was spent in the Script Compiler? Harder: How much in the compilation of the generated C++ code?
• Some statistics on reasons why we rejected bindings/functions – this might also help drive further development of the Script Compiler.

Given that the ScriptCompiler works per TU, we probably need an aggregation step as post-processing.
Lastly, and at a later point, the result could be used by the LSP to highlight compiled and non-compiled bindings differently.