agent: the check command's -m option doesn't handle multiple checks

[deadok22]

The agent check $CHECK_NAME -m command fails with an error when multiple instances of the $CHECK_NAME are configured.

This happens because the check configuration patching to enable memory profiling and the selection of the check instances to run are done in two different places. The former should patch all of the selected check instances' configurations, not just one.

An example of the error message:

...
426 other: 164.70 KiB
Total allocated size: 341.00 KiB
Error: no snapshot data found in /tmp/datadog-agent-memory-profiler671068352/nginx_ingress_controller/5d247b25a3ae9c3b
command terminated with exit code 255