* use my-account/lost-password endpoint url for set password (tbd):
- companion for working on https://github.com/woocommerce/woocommerce/issues/27754
* use more appropriate (new) set-password endpoint
* add version check - use new woo core endpoint if woo version is new enough
* use my-account/lost-password for setting password in checkout signup:
- this has been available forever - no need for a version check
- page will show `Lost password`; looking at options for overriding that
* use more explicit `newaccount` action for set password url if available
* tweak feature gating for checkout signup:
- only available in dev builds (will change soon)
- only available if Woo core 4.7 or newer
- checkout signup relies on fixes in 4.7+ (tbc) to
my-account/lost-password endpoint for setting initial password
- standardise feature gate logic so is consistent, ensure feature is
disabled in API/backend, hide editor option, and disable front end
- add new setting `wcVersion` to allow feature gating on woo version
* fix woo-version feature gate of checkout signup:
- fixed version logic, explicit 4.7.0 reference version
- refactor version compare routine so can be used for woo or WP version
* revamp Woo 4.7+ logic so PHPunit tests aren't dependent on Woo version:
- Woo-version feature gating is implemented at integration layer:
- checkout REST API
- register/override new account email handler