Resolve "Add i18n for email_validation shared example spec"

What does this MR do and why?

The spec/support/shared_examples/features/trial_email_validation_shared_example.rb shared_examples in JH is failing.

This MR is to solve this problem.

The reasons are as follow:

1. JH behaves differently from upstream: email_hint_message does not exist in the Jihu register interface.
2. JH's trial_email_validation=false setting does not take effect.

Solution:

1. Rewrite trial_email_validation_shared_example under JH and add test cases to cover it.
2. Add test cases as jh_related_spec to the filter group in skip_specs.yml.

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Closes #1541 (closed)