DataLinks: Default to url escaped variable interpolation format

[torkelo]

When Datalinks contain variables and they are interpolated they are not by default uri escaped.

the templateSrv replace function takes a default interpolation format as third argument so if we passed percentencode

here: https://github.com/grafana/grafana/blob/master/public/app/features/panel/panellinks/link_srv.ts#L325

and here: https://github.com/grafana/grafana/blob/master/packages/grafana-data/src/field/fieldOverrides.ts#L429

It should solve the problem

[meberli]

had same issue with '++' in variable beeing replaced by %20 instead of %2B