Interface proposal : pull request 5

[yoann-heitz]

This is the last pull request for the interface proposal. It adds the --output-plugin option in rocprof and instructions to overload user-defined flushing functions (that respect some specifications).

An example of a CTF plugin can be found here : https://github.com/dorsal-lab/rocprofiler_ctf_plugin/tree/rocm-4.3.x-PR5 (be sure to use the rocm-4.3.x-PR5 branch for tests).

Relative to the fourth pull request, this one starts at commit 86d43f3