Split 1.17 module into 1.17-common, 1.17, and 1.17.1

[willkroboth]

This PR takes the old commandapi-1.17 module and splits it into three modules: commandapi-1.17-common, commandapi-1.17, and commandapi-1.17.1.
This is necessary because the field MinecraftServer.resources (accessed in reloadDataPacks()) is mapped to two different names (aB and aC) for the two versions 1.17 and 1.17.1. This caused the following exception on a 1.17 Spigot Server:

[15:14:47] [Server thread/INFO]: [CommandAPI] Reloading datapacks...
[15:14:47] [Server thread/WARN]: [CommandAPI] Task #2 for CommandAPI v8.4.1 generated an exception
java.lang.NoSuchFieldError: aB
    at dev.jorel.commandapi.nms.NMS_1_17_R1.reloadDataPacks(NMS_1_17_R1.java:647) ~[?:?]
    at dev.jorel.commandapi.CommandAPI.lambda$onEnable$0(CommandAPI.java:186) ~[?:?]
    at org.bukkit.craftbukkit.v1_17_R1.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at org.bukkit.craftbukkit.v1_17_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:400) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at net.minecraft.server.MinecraftServer.b(MinecraftServer.java:1252) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at net.minecraft.server.dedicated.DedicatedServer.b(DedicatedServer.java:436) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:1200) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at net.minecraft.server.MinecraftServer.x(MinecraftServer.java:1027) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at net.minecraft.server.MinecraftServer.lambda$0(MinecraftServer.java:307) ~[spigot-1.17.jar:3170-Spigot-a483d2c-ec116f6]
    at java.lang.Thread.run(Thread.java:831) [?:?]

It seems that this is the only difference relevant to the CommandAPI between 1.17 and 1.17.1, though if other differences are found, these classes can definitely be expanded. To cut down redundant code, commandapi-1.17-common contains almost all the NMS methods except for reloadDataPacks(), which is implemented identically in commandapi-1.17 and commandapi-1.17.1, but mapped differently by specialsource.

To allow commandapi-1.17 and commandapi-1.17.1 access commandapi-1.17-common both before and after it is remapped, they depend on both the mojang mapped and unmapped versions of Spigot 1.17.1-R0.1-SNAPSHOT.

I tried to match the code style and project layout, but I'm not sure if I got the annotations correct on the NMS classes. Feel free to change anything that's not quite right!

[JorelAli]

Thanks for this - I was not aware Maven would let you compile against two versions of the same dependency.

The NMS class requires a method compatibleVersions() to be implemented, this will need to be implemented in each submodule (i.e. in 1.17 and 1.17.1):

@Override
public String[] compatibleVersions() {
    return new String[] { "1.17", "1.17.1" };
}

[JorelAli]

Each NMS module should have a test folder with a SafeReflect.java file. This is used for compile-time reflection checks for code that has reflection. The reloadDatapacks() method uses reflection to modify CustomFunctionManager's command dispatcher.

Although we can already assert this won't fail, I'd still like the 1.17 module and 1.17.1 module to independently have this reflection check (as opposed to just commandapi-1.17-common), because the compile-time reflection checks use the spigot libraries used for compile time (i.e. it'll perform reflection checks against spigot 1.17 for commandapi-1.17 and perform reflection checks against spigot 1.17.1 for commandapi-1.17.1).