plugin change: make interval, cache timeout & max data points options in plugin.json, remove query.options component feature, add help markdown feature and toggle for data sources

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Prometheus: Fix actual step computation logic when a min_step is specified and the range is longer than min_step * 11000. (#9109)

fix: changed modal to fixed positioned, this change makes modal maintain scroll position, fixes #8800

elasticsearch: changed ad hoc filters from using term filters to using phrase match queries, closing #9095

Add support of non_negative_difference() function from InfluxDB 1.3
https://docs.influxdata.com/influxdb/v1.3/administration/differences/#functions

Raw query results would return as expected. But when appending new series to pointsBySeries map, order of keys is random. So I've added a list to keep track of series order. Should implement FIFO rules.

Azure's MySQL implementation appears to always respond with an Authentication Method Switch Request Packet requesting `mysql_native_password` auth even though the client's initial Handshake Response already included the native password credentials.

Most MySQL client libraries support this but Golang's go-sql-driver/mysql requires the `allowNativePasswords` DSN parameter set to enable it. Without this parameter, Grafana fails to authenticate to the database with the error message "this user requires mysql native password authentication."

References:

* https://web.archive.org/web/20160814002743/http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::AuthSwitchRequest
* https://web.archive.org/web/20160814002743/http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::HandshakeResponse
* https://github.com/go-sql-driver/mysql#user-content-allownativepasswords

Adds back feature that adds 'sep=;' text that excel needs in a csv file.
Also adds toggle to make this optional if exporting to other spreadsheet
programs. Fixes #9083.