Add volume filters to system prune

This change was missed in pull/8689. Now that volume pruneing supports
filters system pruneing can pass its filters down to the volume
pruneing. Additionally this change adds tests for the following components

* podman system prune subcommand with `--volumes` & `--filter` options
* apiv2 api tests for `/system/` and `/libpod/system` endpoints

Relates to #8453, #8672

Signed-off-by: Baron Lenardson <lenardson.baron@gmail.com>

libpod/filters/helpers.go

@@ -0,0 +1,20 @@
+package lpfilters
+
+import (
+	"net/url"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+func ParseFilterArgumentsIntoFilters(filters []string) (url.Values, error) {
+	parsedFilters := make(url.Values)
+	for _, f := range filters {
+		t := strings.SplitN(f, "=", 2)
+		if len(t) < 2 {
+			return parsedFilters, errors.Errorf("filter input must be in the form of filter=value: %s is invalid", f)
+		}
+		parsedFilters.Add(t[0], t[1])
+	}
+	return parsedFilters, nil
+}