Code Insights: [BE] Add filters field in `createLineChartSearchInsight` mutation

Created by: vovakulikov

At the moment we can't create insight with a predefined filters value. But we have a case when this creation is needed. You can create insight from the drill-down filter panel. Because of this issue FE at the moment doesn't support this functionality.

A possible workaround for FE in case if BE couldn't support this: call createInsight mutation first and then call updateLineChart mutation where we have filters field in input type. @unclejustin FYI.

Current state of Input type for createLineChartSearchInsight mutation.

"""
Input for a line chart search insight.
"""
input LineChartSearchInsightInput {
    """
    The list of data series to create (or add) to this insight.
    """
    dataSeries: [LineChartSearchInsightDataSeriesInput!]!

    """
    The options for this line chart.
    """
    options: LineChartOptionsInput!

    """
    The dashboard IDs to associate this insight with once created.
    """
    dashboards: [ID!]
}