osd: Refine implementation that sets built-in profile parameters.

osd: Refine implementation that sets built-in profile parameters.

mclock clients are categorized into client, background_recovery and
background_best_effort. Each client category is required to specify
the mclock parameters like reservation, weight and limit. Therefore,
a simple structure (ClientAllocs) is introduced that encapsulates the
mclock parameters and is used to store those parameters for each client
category.

Other changes:
 - The "high_client_ops" profile is now set as the default profile
    instead of the "balanced" profile.
 - Replace "Stringify" with std::to_string().

Signed-off-by: Sridhar Seshasayee <sseshasa@redhat.com>