src.ctf.fs: modernize read_src_fs_parameters

src.ctf.fs: modernize read_src_fs_parameters

Change the input parameter `params` to be bt2::ConstMapValue.  Change
the return type to be of a new structure type containing all processed
parameters, rather than using output parameters and rather than setting
the clkClsCfg inside the ctf_fs object directly.  Change the type of the
parameters of ctf_fs_component_create_ctf_fs_trace and other helper
functions accordingly.

Change-Id: I2ba5aca22f907ffcfbdd19c8d8077e17d0c47a71
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8421
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>