lisa._kmod: Make use of kmod VFS to configure features

A previous patch adds support for a virtual file system (VFS)
for the lisa module. This VFS allows to configure the module
features at runtime.
Make use of this VFS to configure the desired features. Features
that have parameters can be configured from a notebook with:
"""
features = {
  "lisa__perf_counter": {
    "generic_counters":
      ["cpu_cycles", "l1d_cache", "inst_retired"]
  }
}
ftrace_coll = FtraceCollector(target, ..., kmod_features=features)
"""

Original-author: Beata Michalska <beata.michalska@arm.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>