refactor(oas3): improve servers component layout and structure

[hariswhdn]

Description

Refactored the OAS3 servers component to improve layout structure and user interface consistency.

Changes:

• Reorganized servers component JSX structure by wrapping the select label and variables UI in a shared container div for improved semantic grouping
• Redesigned visual hierarchy of server selection controls with proper spacing and alignment
• Added comprehensive styling for .schemes-server-container with flexbox layout
• Enhanced computed URL display with improved typography and spacing
• Improved server variables table styling with better padding and visual hierarchy
• Added responsive styling for server selection dropdowns with vendor-consistent appearance

Motivation and Context

The previous server component layout lacked proper visual grouping between the server selector, computed URL, and server variables. This change improves the user interface by:

• Creating visual relationship between related controls
• Improving accessibility through better semantic HTML structure
• Enhancing readability of server variable configurations
• Providing consistent styling across different screen sizes

Relates to OAS3 server handling improvements.

How Has This Been Tested?

Manual testing in development environment:

• Tested with Petstore API spec containing server variables
• Verified server selection dropdown functionality
• Confirmed server variable inputs (enum select and text input) work correctly
• Tested computed URL display with variable substitution
• Validated responsive layout on various screen sizes (desktop, tablet)
• Confirmed no visual regressions in browser console

Screenshots (if appropriate):

Before	After

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Improvements (misc. changes to existing features)
• Bug fixes (non-breaking change which fixes an issue)
• Features (non-breaking change which adds functionality)
• Dependency changes (any modification to dependencies in package.json)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can and should be tested by unit and/or integration tests.
• My changes can not or do not need to be tested.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.