Painting command executors are defined within the "Painting" namespace,
allowing us to remove this prefix from their names.
This commit performs the following renamings:
- Painting::PaintingCommandExecutor to Painting::CommandExecutor
- Painting::PaintingCommandExecutorCPU to Painting::CommandExecutorCPU
- Painting::PaintingCommandExecutorGPU to Painting::CommandExecutorGPU
Separating the recorder list from the painter will allow us to save it
for later execution without carrying along the painter's state. This
will be useful once we have a separate thread for executing painting
commands, to which we will have to transfer commands from the main
thread.
Preparation for https://github.com/SerenityOS/serenity/pull/23108