And additional profiling zone markers.

In accordance with the CSS specs.

Employ it around the library for extra debug checks (only with rtti enabled).

…t contexts, see mikke89#520

…iling markers, solves mikke89#516

Tracy client can now be included in one of three ways, in prioritized order:
1. Using target Tracy::TracyClient from parent project.
2. As a config package.
3. With Tracy source files located in 'Dependencies/Tracy'.

Adds three new CMake options:
- `RMLUI_TRACY_PROFILING`: Enable profiling, replaces the old option `ENABLE_TRACY_PROFILING`.
- `RMLUI_TRACY_MEMORY_PROFILING`: Overloads global operator new/delete for memory inspection.
- `RMLUI_TRACY_CONFIGURATION`: Only relevant for multi-config generators. If enabled, adds Tracy as a separate configuration, otherwise adds Tracy to all configurations.

Update tracy integration, allow parent projects to include RmlUi profiling markers

…see mikke89#521

…ikke89#522)

…ugh)