Add handling for PR as a US state in terminal locations API

[deepakpathania]

Similar to: Automattic/woocommerce-payments#10349

Changes proposed in this Pull Request:

• Return PR as a state and US as the country in case PR is set as the country for the terminal locations endpoint.

Testing instructions

• Tests should pass.
• Get location API should return PR as state and US as country in case PR is the location.

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• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

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Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)