mgr/cephadm: support for regex based host patterns

mgr/cephadm: support for regex based host patterns

For example, with hosts vm-00, vm-01, and vm-02
I was able to provide the placement

service_type: node-exporter
service_name: node-exporter
placement:
  host_pattern:
    pattern: vm-00|vm-02
    pattern_type: regex

and it placed the node-exporter daemons on vm-00
and vm-02 but not vm-01. Obviously there are more
advanced scenarios that justify this than listing
two hosts, but using "|" as an OR like that is an
example of something you can't do with the fnmatch
version of the host pattern

Signed-off-by: Adam King <adking@redhat.com>