Allow variables (non-numericals) in Limit field on Query Builder

[vstariradev]

We have a Grafana logs dashboard where one of the fields our devs can set is the LIMIT of a SELECT query. In order to move entirely to Query Builder search (and allow context loading) I need to be able to translate the $limit variable set in the dashboard variables to the Limit field of the Query Builder.
Currently I only numbers can be entered in the Limit field, which makes sense but doesn't fit a popular use case IMO where we want LIMIT to be set by a variable.