VAT Info: Use string interpolation for tax names

[sirbrillig]

Proposed Changes

This is a follow-up to #74538 which localized the "VAT" term in checkout. Because the name of VAT changes based on country, it would be better to use a localized term. In #73686 we modified the labels for the VAT form use use the more generic term "Business Tax", but this is still a little unclear.

In this PR we switch each of these labels to replace "Business Tax" with the selected country's term for VAT (eg: "GST", "CT", etc.) on the user-level VAT form.

NOTE: This can only localize once a country is selected... which means that the button to reach the form will always read "Add VAT details" before the user reaches the form. To resolve that case, we use the useGeoLocationQuery() hook to provide a fallback country.

This is part of https://github.com/Automattic/payments-shilling/issues/1475 and https://github.com/Automattic/payments-shilling/issues/1474

Screenshots

Testing Instructions

• Visit /me/purchases/vat-details.
• Select a country that uses the term "VAT" like the United Kingdom.
• Verify that all the form labels use the word "VAT".
• Select a country that uses a different term like Australia, which uses "GST".
• Verify that all the form labels use the word "GST" (except for the title, which won't change until the details are saved).
• Visit /me/purchases/billing and set your geolocation (eg: using a VPN) to somewhere that is in a country that does not use "VAT" (eg: Australia).
• Verify that the button at the bottom reads "Add GST details".

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-62804

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-62804&env=jetpack

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~388 bytes added 📈 [gzipped])

name            parsed_size           gzip_size
purchases           +1370 B  (+0.1%)     +388 B  (+0.1%)
site-purchases       +440 B  (+0.0%)     +108 B  (+0.0%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[a8ci18n]

This Pull Request is now available for translation here: https://translate.wordpress.com/deliverables/7892983

Thank you @sirbrillig for including a screenshot in the description! This is really helpful for our translators.

[spraveenitpro]

Functional Testing:

Before Applying the patch:

After applying the patch - Great Britain

After applying the patch - Australia

After applying the patch with VPN pointing to Australia

[spraveenitpro]

LGTM, excellent implementation of useQuery TIL!

[a8ci18n]

Translation for this Pull Request has now been finished.