Added carrier code to ID to distinguish shipping methods [backport 2.1]

[peterjaap]

Added carrier code to ID to distinguish shipping methods with the same method name but differing carrier code

Shipping method radios have duplicate element IDs on cart page, which makes it impossible to select the second method.

Description

Make the element ID unique by adding in the carrier code into the ID.

Fixed Issues (if relevant)

1. Shipping method radios have duplicate IDs on cart page #10795: Shipping method radios have duplicate IDs on cart page

Manual testing scenarios

1. Create a shipping method with a unique carrier name but a method name that is in use, such as 'freeshipping' (make sure to of course enable the freeshipping option and have it appear in the checklist).

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)