Improve command buffer

[mwestphal]

Is your feature request related to a problem? Please describe.
https://github.com/f3d-app/f3d/pull/1899/files Introduces a command buffer that is required for console interaction.
This buffer is very simple and contains a single command. It may be better to improve it, make it contains multiple commands and rely on it for more usecases instead of running command synchronously.

Describe the solution you'd like

• Add a proper (internal) API for the command buffer
• Support multiple command (AddCommandBuffer, ClearCommandBuffer)
• Use it everywhere it makes sense