workaround compiler bug involving reflective calls

[fwbrasil]

Fixes #542

Problem

The compiler tries to infer the type of the reflectiveCalls but fails with an NPE when the import is inside the nested structural value.

Solution

Move the import to the upper level and use a mechanism to avoid unused import warnings.

Checklist

• Unit test all changes
• Update README.md if applicable
• Add [WIP] to the pull request title if it's work in progress
• Squash commits that aren't meaningful changes
• Run sbt scalariformFormat test:scalariformFormat to make sure that the source files are formatted

@getquill/maintainers