Allow for combination of both handlers

Currently, there is two available handlers: the COMMAND_TO_SERVER handler, and the REGULAR handler. The problem is that, when using the REGULAR handler, you loose the ability to load balance servers. It would be nice to have a combination between the two, where you would do something like:
```hcl
many-to-many-handler {
command {
# Commands that can be used
commands=[
lobby,
hub
]
# List of servers
servers=[
lobby,
lobby1,
hub
]
# Send Mode Formula
# RANDOM: It will send the player to a random server among the configured ones
# FIRST_AVAILABLE: It will send the player to the first available server
# EMPTIEST: Send the player to the server with the least amount of players
send-mode=RANDOM
}

command {
# Commands that can be used
commands=[
bedwars,
bw
]
# List of servers
servers=[
bedwars1,
bedwars2
]
# Send Mode Formula
# RANDOM: It will send the player to a random server among the configured ones
# FIRST_AVAILABLE: It will send the player to the first available server
# EMPTIEST: Send the player to the server with the least amount of players
send-mode=EMPTIEST
}
}
```

Look at the existing handlers in the codebase, likely in a handlers package. Understand how COMMAND_TO_SERVER and REGULAR handlers are implemented. The feature requires combining their logic to support command-based load balancing. Check for configuration parsing and server routing logic. Test by building the plugin and verifying the new HCL configuration works with Velocity.

Rédigé par le modèle d'indexation à partir du texte de l'issue.