Added support for WooCommerce Multilingual Standalone Version

[5um17]

Description

WooCommerce Multilingual comes in two versions: Standalone Version and Full Features with WPML.

In PR #4462, we added support for Full Features with WPML, but Standalone Version was released after these changes. That is currently not working with WP Rocket. You can view the customer report WCML shows default currency, regardless of location

These changes were suggested by @strategio

Documentation

User documentation

• Added support for WooCommerce Multilingual Standalone Version

Technical documentation

• Removed the ICL_SITEPRESS_VERSION constant that is defined only in WPML, and retained WCML_VERSION defined in WooCommerce Multilingual.

Type of change

• [x] Enhancement (non-breaking change which improves an existing functionality).

Checklists

Feature validation

• [x] I validated all the Acceptance Criteria. If possible, provide sreenshots or videos.
• [x] I triggered all changed lines of code at least once without new errors/warnings/notices.

Documentation

• [x] I prepared the user documentation for the feature/enhancement and shared it in the PR or the GitHub issue.
• [x] I prepared the technical documentation if needed, and shared it in the PR or the GitHub issue.

Code style

• [x] I wrote self-explanatory code about what it does.
• [x] I did not introduce unecessary complexity.