Add support of dynamic labels for SpecFlow integration

[neparij]

What is the current behavior?

There is no way to create custom labels. The tag was created on any custom labels (ex.: '@layer:e2e')

What is the expected behavior?

Custom label containing only 1 colon char should be recognised as custom label (ex.: '@layer:e2e' should create label named 'layer' with value 'e2e')

[baev]

btw Allure TestOps has it's own labels-from-tags processing: try to add tag @allure.id=123 or @allure.label.layer: api

For report users there is no point to add custom labels as everything custom is ignored by default

[delatrie]

Custom labels can be created using a pattern defined in allureConfig.json (specflow/labels/label). Also, the tag-to-label conversion works in Allure Report now, starting from 2.27.0.