Improve code readability and layout of vulnerability report filters

What does this MR do?

On the vulnerability report page (we have 3 different places where it's shown):

Project level	Group level	Instance level

There are filter dropdowns that will filter the vulnerability list:

This MR does the following:

1. Each dropdown has an option count threshold that, if exceeded, will show a search box. The logic for this has been improved.

2. Improved the space usage of the filters to avoid text truncation.

3. Changed from using <component :is="componentType">, to using the actual component.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is refactor work.
• [-] 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