Add validation framework for imposing specific rules for configuration values

[csutherl]

This PR implements a proof-of-concept that enhances the configtest command with validation capabilities, focusing on port configuration as a valuable starting point from dev-list discussion. It includes the framework and a single validation class, PortValidator, for community review. It also adds a LifecycleListener that is capable of stopping the startup process when there are validation failures. This minimal/phase 1 implementation includes the listener as I thought it was a valuable addition and was pretty straightforward to implement. Therefore Phase 3 would just be the SPI implementation, if we want to go that route.

Note: The configtest behavior hasn't changed unless you use the --validate-only option to produce validation output instead of the typical server startup attempt. There's also a new command in Catalina for config-validate for ease of use.

Port validation detects:

• Port conflicts (already in use)
• Invalid port numbers (< 0 or > 65535)
• Duplicate port assignments across connectors
• Privileged ports (< 1024) without root access
• Default/insecure shutdown commands
• AJP connectors missing required 'secret' attribute
• AJP connectors listening on all interfaces (0.0.0.0)

Future enhancements may include:

• Additional validators (file resources, JNDI, security, known config issues)
• ServiceLoader plugin architecture for custom validators
• Configurable validator ordering
• Overrides for default validator behavior

[csutherl]

@ChristopherSchultz did you have any input about whether or not this addresses the concern you mentioned on the list thread?