MFC 300253: Remove dangling references to rman_await_resource().

This function was removed when RF_TIMESHARE was removed a couple of years
ago.

MFC r268780

Nuke the never-used RF_TIMESHARE feature, reducing the complexity of the
code. The consensus on arch@ is that this feature might have been useful
in the distant past, but is now just unnecessary bloat.

The int_rman_activate_resource() and int_rman_deactivate_resource()
functions become trivial, so manually inline them.

The special deferred handling of RF_ACTIVE is no longer needed in
reserve_resource_bound(), so eliminate the associated code at the
end of the function.

These changes reduce the object file size by more than 500 bytes on i386.

Update the rman.9 man page to reflect the removal of the RF_TIMESHARE
feature.

MFC r268780

Nuke the never-used RF_TIMESHARE feature, reducing the complexity of the
code. The consensus on arch@ is that this feature might have been useful
in the distant past, but is now just unnecessary bloat.

The int_rman_activate_resource() and int_rman_deactivate_resource()
functions become trivial, so manually inline them.

The special deferred handling of RF_ACTIVE is no longer needed in
reserve_resource_bound(), so eliminate the associated code at the
end of the function.

These changes reduce the object file size by more than 500 bytes on i386.

Update the rman.9 man page to reflect the removal of the RF_TIMESHARE
feature.