Description

This issue resolves gravityforms/backlog#5741 by doing the following:

1. Updates how the checksum is extracted from the checksum string regardless of the checksum string length.
2. Depending on the length, it decides the encryption method used to generate the checksums and use when checking the files against the checksums.

Testing instructions

1. Download the latest gravityforms build from gravityform.com (don't use the repo, we need that downloadable version in particular)
2. Use this branch for gravitycli
3. Make sure gravity cli is activated
4. From local, right click on the website and from the menu click "open site shell"
5. In the terminal type cd app/public/wp-content/plugins/gravityforms
6. Then type this command wp gf tool verify-checksums
7. After the command has been executed (it takes a couple of seconds) you should get the following success message :"Success: Gravity Forms install verifies against checksums."

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