Support specific linear query for new `getMultipleLinearIntValues`

[wu-sheng]

In the current query protocol, you have the only option to provide the total line number. As a result, such as for percentile, you have to query P50 if you want to other metrics, such as P50->P99 or P50-P90.

    # Query the type of metrics including multiple values, and format them as multiple linears.
    # The seq of these multiple lines base on the calculation func in OAL
    # Such as, should us this to query the result of func percentile(50,75,90,95,99) in OAL,
    # then five lines will be responsed, p50 is the first element of return value.
    getMultipleLinearIntValues(metric: MetricCondition!, numOfLinear: Int!, duration: Duration!): [IntValues!]!

This new query could leverage the existing DAO feature, but filter the query result including specific linear(s) only. We could add linearIndex as a parameter.

    getSubsetOfMultipleLinearIntValues(metric: MetricCondition!, linearIndex: [Int!]!, duration: Duration!): [IntValues!]!

I will try to work on this. If any of @apache/skywalking-committers wants to lead, please let me know.