Allow wildcards in secrets environment scope dropdown

What does this MR do and why?

Implements #470454 (closed)

We want to allow users to use wildcards in the environments dropdown for Secrets Manager. The component already has this feature, we just need to enable it.

When creating a scoped environment, CiEnvironmentsDropdown will emit the same event (select-environment) as when a predefined environment is selected from the dropdown.

Note: The Secrets Manager uses mock data for the frontend while integration with the backend is not yet available.

MR acceptance checklist

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Screenshots or screen recordings

Screen_Recording_2024-07-03_at_13.42.01

How the environment label looks like when you create the secret:

How to set up and validate locally

1. Enable the feature flag.

   Feature.enable(:ci_tanukey_ui)

2. Visit path-to-project/-/secrets/new
3. The environments dropdown should allow you to create scoped environments by typing them in the search bar and clicking Create wildcard.