Move capabilities check behind admin_init and is_admin

[BrianHenryIE]

Proposed changes

In the ECommerce constructor capabilities checks are being used. In the data module, if the capabilities transient is absent a request is made to Hiive to update it. This expires after four hours.

From what I read, the capabilities checks here are running on every request, meaning every site is polling Hiive for capabilities every four hours.

This change moves the check behind admin_init and is_admin so the capabilities are only fetched when an admin is accessing /wp-admin. The actions and filters that were guarded by the capabilities are all related to admin UI changes (most obviously printing HTML).

8b9c371

https://jira.newfold.com/browse/PRESS0-1016

Type of Change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Video

Checklist

• I have read the CONTRIBUTING doc
• I have viewed my change in a web-browser
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

• We are working on related changes in the data module to store the capabilities in an option rather than a transient, and in Hiive to push changes to the capabilities so polling is not necessary.
• It's unclear to me if the failing tests are caused by this change. One of them is ~expected button not to exist, and the other could not find the my-products table.