Add Falcon::CompositeServer.

[samuel-williams-shopify]

Introduce Falcon::CompositeServer for hosting multiple server instances in a single worker.

Types of Changes

• New feature.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[Copilot]

Pull request overview

This PR introduces Falcon::CompositeServer to manage and run multiple Falcon::Server instances within a single worker, along with tests and release notes.

Changes:

• Add Falcon::CompositeServer to coordinate running multiple named Falcon::Server instances and aggregate their statistics.
• Add a focused test suite for Falcon::CompositeServer to validate multi-endpoint handling, stopping behavior, and statistics output.
• Wire the new class into the public falcon entrypoint and document the new feature in releases.md.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
lib/falcon/composite_server.rb	Implements Falcon::CompositeServer with run, statistics_string, and detailed_statistics to manage multiple server instances and expose per-server stats.
test/falcon/composite_server.rb	Provides tests covering multi-server management, request handling across endpoints, stopping behavior, and statistics for zero, one, and multiple servers.
lib/falcon.rb	Exposes Falcon::CompositeServer via the main falcon require, making it part of the public API.
releases.md	Notes the introduction of Falcon::CompositeServer in the unreleased changelog section.