[1.21.1] Relax extensible enum coherence checks for extensible enums without custom entries

[XFactHD]

This PR relaxes the coherence checks on extensible enums to allow a client/server with an extensible enum without additional entries to connect to a server/client with the respective enum not made extensible. This ensures that a NeoForge version which makes a new enum extensible is network-compatible with the previous NeoForge version as long as no mod adds additional entries to the affected enum. With the current implementation, any additional enum being made extensible and marked as @NetworkedEnum would break network compatibility with the previous version, regardless of any mod actually making use of the extensibility.

[neoforged-pr-publishing]

• Publish PR to GitHub Packages

Last commit published: f6ca17a4f50739cc89085b2e627307b270dd7675.

PR Publishing

The artifacts published by this PR:

• 📦 net.neoforged:testframework:21.1.65-pr-1559-relax_enum_checks
• 📦 net.neoforged:neoforge:21.1.65-pr-1559-relax_enum_checks

Repository Declaration

In order to use the artifacts published by the PR, add the following repository to your buildscript:

repositories {
    maven {
        name 'Maven for PR #1559' // https://github.com/neoforged/NeoForge/pull/1559
        url 'https://prmaven.neoforged.net/NeoForge/pr1559'
        content {
            includeModule('net.neoforged', 'testframework')
            includeModule('net.neoforged', 'neoforge')
        }
    }
}

MDK installation

In order to setup a MDK using the latest PR version, run the following commands in a terminal.
The script works on both *nix and Windows as long as you have the JDK bin folder on the path.
The script will clone the MDK in a folder named NeoForge-pr1559.
On Powershell you will need to remove the -L flag from the curl invocation.

mkdir NeoForge-pr1559
cd NeoForge-pr1559
curl -L https://prmaven.neoforged.net/NeoForge/pr1559/net/neoforged/neoforge/21.1.65-pr-1559-relax_enum_checks/mdk-pr1559.zip -o mdk.zip
jar xf mdk.zip
rm mdk.zip || del mdk.zip

To test a production environment, you can download the installer from here.

[pupnewfster]

Code looks fine (though I have not personally tested the functionality)

[neoforged-automation]

@XFactHD, this pull request has conflicts, please resolve them for this PR to move forward.