Update to sqlutil helpers

[iwysiu]

In https://github.com/grafana/cloud-data-sources/issues/94 some standalone sql helper functions were copied to sqlutil in the plugin sdk. Use those here instead to deduplicate code.

[gabor]

NOTE: it seems the macros.go in pluginsdk, at the time of writing this comment, corresponds to macros.go in sqlds at commit cd68d26e53cdfd799f700d4623f9f3c946101fb3 : https://github.com/grafana/sqlds/commit/cd68d26e53cdfd799f700d4623f9f3c946101fb3

• it contains the quick exit from the loop comment that was added in that comment
• it does not contain the when we are inside an argument comment that was added in the next macros.go-touching commit ( https://github.com/grafana/sqlds/commit/6cccadd0867f24e02cf64131f2bf2fd252fc1530 )

since that commit in sqlds, there has been changes done to macros.go in sqlds, so those changes will have to be applied to the pluginsdk version too.