[Cashtab] Webpack upgrade part 9, fix import order

Summary:
T1682

Latest version of webpack won't tolerate import statements that are not at the top of the file. Cashtab has some of these.

This diff corrects the issue.

Test Plan: Confirm these changes remove code from above import statements. The app will still not work as css errors need to be patched in the next step.

Reviewers: #bitcoin_abc, kieran709

Reviewed By: #bitcoin_abc, kieran709

Differential Revision: https://reviews.bitcoinabc.org/D11249