Allow filtering metrics with custom properties

config/metrics/schema/internal_events.json

...internal_event_instrumentation/metric_definition_guide.md

...l_analytics/internal_event_instrumentation/quick_start.md

...nt_total_cvs_on_sbom_change_with_extra_filters_weekly.yml

lib/gitlab/internal_events.rb

lib/gitlab/tracking/event_validator.rb

scripts/internal_events/cli/flows/metric_definer.rb

...l_events/events/event_with_multiple_custom_properties.yml

...ts/metrics/user_id_28d_single_event_custom_key_filter.yml

...nts/metrics/user_id_7d_single_event_custom_key_filter.yml

spec/fixtures/scripts/internal_events/new_metrics.yml

spec/lib/gitlab/internal_events_spec.rb

spec/lib/gitlab/tracking/event_validator_spec.rb