One DAMON context can have multiple monitoring targets, and DAMOS schemes
are applied to all targets.  In some cases, users need to apply different
scheme to different targets.  Retrieving monitoring results via DAMON
sysfs interface' 'tried_regions' directory could be one good example. 
Also, there could be cases that cgroup DAMOS filter is not enough.  All
such use cases can be worked around by having multiple DAMON contexts
having only single target, but it is inefficient in terms of resource
usage, thogh the overhead is not estimated to be huge.

Implement DAMON monitoring target based DAMOS filter for the case.  Like
address range target DAMOS filter, handle these filters in the DAMON core
layer, since it is more efficient than doing in operations set layer. 
This also means that regions that filtered out by monitoring target type
DAMOS filters are counted as not tried by the scheme.  Hence, target
granularity monitoring results retrieval via DAMON sysfs interface becomes
available.

Link: https://lkml.kernel.org/r/20230802214312.110532-9-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>