Add PHP plugin and enhance plugin infrastructure

[trevorphillipscoding]

• Implement PHP plugin to manage PHP installations, including version fetching and downloading.
• Introduce ReadAPIBody utility to limit API response size for plugins.
• Update Go and Node plugins to utilize the new API reading utility.
• Add concurrent test for global state updates to ensure no lost writes.
• Enhance shim registration tests to report collisions accurately.
• Create a local testing script for end-to-end testing of the nvy CLI.
• Update documentation and tests to reflect new PHP plugin functionality.

Description

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• New plugin/runtime support

Related Issues

Testing

• Tested on macOS
• Tested on Linux
• Added/updated tests
• All existing tests pass (make test)

Checklist

• My code follows the project's style guidelines
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation (README, etc.) if needed
• My changes generate no new warnings or errors
• I have run make lint and addressed any issues

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