Implement dynamic form control component

What does this MR do?

Add DynamicFields component

This adds a dynamic form field component, to be used in the SAST Configuration UI.

So far, this component is only able to render a single type of form field: a text input (via the FormInput component). Future iterations will add support for more types.

This component is driven by an array of configuration entities (in fact, a SastCiConfigurationEntity from GraphQL), each representing a configurable variable when setting up SAST scanning for a project. In a follow-up MR, this array will be provided by the GraphQL query Project.sastCiConfiguration.

Addresses #231370 (closed).

Screenshots

Note that:

1. this isn't actually used anywhere yet, so this screenshot is just for context of what it can look like
2. this component doesn't actually implement any visible UI itself, since it delegates to FormInput

Draft

This MR is in Draft, as it's blocked by !37812 (merged).

Feature flag

While this component isn't used anywhere yet, it will be used in the SAST Configuration UI page, which itself is behind the sast_configuration_ui feature flag.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done