[BUG][GO] only import reflect when using it

[perhallgren]

The api.mustache template only uses the reflect package if there is a query parameter which isCollectionFormatMulti. The import for the reflect package is however added if any parameter is isCollectionFormatMulti.

If the parameter which isCollectionFormatMulti e.g. is in the body instead of the query, this leads to the import being part of the generated code but not used and the code does not compile.

This updates reworks the import handling for the reflect package so that it is only added if there is a query parameter which isCollectionFormatMulti.

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[perhallgren]

Pings for technical committee: @antihax @grokify @kemokemo @jirikuncar @ph4r5h4d @lwj5

[wing328]

thanks for the PR.

lgtm. let's give it a try