## Is your feature request related to a problem?

As a team accumulates data, they will have events/properties that are no longer in use that clutter their app.

Example from our team:
![image](https://user-images.githubusercontent.com/148820/143202334-42d73ab6-13be-4661-ba7a-83c86788b9e8.png)


## Describe the solution you'd like

Under event/properties stats allow 'hiding' events/properties from view.

## Describe alternatives you've considered

Alternatively, go the route of "verified" events/properties (as He@p) does - show those first. See also https://help.heap.io/category/heap-administration/data-governance/

## Additional context

Note: Existing reports, etc should still work well even with 'removed' events/properties.

Related: https://github.com/PostHog/posthog/issues/7126

#### *Thank you* for your feature request – we love each and every one!

posthog/api/property_definition.py
search = serializers.CharField(
        help_text="Searches properties by name",
        required=False,
        allow_blank=True,
    )
    type = serializers.ChoiceField(
        choices=["event", "person", "group"],
        help_text="What property definitions to return",
        default="event",
    )
    group_type_index = serializers.IntegerField(
        help_text="What group type is the property for. Only should be set if `type=group`",
        required=False,
    )
    properties = serializers.CharField(
        help_text="Comma-separated list of properties to filter",
        required=False,
    )
    is_numerical = serializers.BooleanField(
        help_text="Whether to return only (or excluding) numerical property definitions",
        required=False,
        allow_null=True,
        default=None,
    )
    
    is_feature_flag = serializers.BooleanField(
        help_text="Whether to return only (or excluding) feature flag properties",
        required=False,