Add a status field indicating if a server is deprecated or active (#210) - #2

The following PR adds a new server `status` field to support the status
of servers, like deprecated or active

Details:
* Add status field to server.json schema with 'active' and 'deprecated'
values
* Update OpenAPI spec to include status field in Server responses
* Add ServerStatus enum and field to Go model structs
* Update examples to demonstrate status field usage (`active` and
`deprecated`)

Since this is my first PR there's a good chance I might have missed
something so I'll appreciate any feedback to make this and any PRs in
the future easier for you to review 😃

Fixes: #181

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The main goal is to have a way for server authors to notify registry
consumers that a server may no longer be maintained and shouldn't be
considered for using.

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

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Signed-off-by: Radoslav Dimitrov <[email protected]>
Co-authored-by: Tadas Antanavicius <[email protected]>