[Forge] SideOnly: Disable checking inside methods marked with specific annotation

[WeAthFoLD]

First of all awesome plugin! Thank you for the efforts creating this >3

There is one case of valid sideonly usage:

void someFunc() {
    if (getSide() == Side.CLIENT)
        someClientOnlyMethod();
}

@SideOnly(Side.CLIENT)
void someClientOnlyMethod() { ... }

where getSide() effectively returns FMLCommonHandler.INSTANCE.getEffectiveSide().

There are possible variations which are essentially the same:

void someFunc() {
    if (isClient())
        someClientOnlyMethod();
}

// Maybe wrapped in some utility class
boolean isClient() { return getSide() == Side.CLIENT; }

@SideOnly(Side.CLIENT)
void someClientOnlyMethod() { ... }

Since detecting this kind of usage can be difficult, I suggest using certain annotation (e.g. SuppressWarning("sideonly") on methods that have this kind of usage.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[DenWav]

I've thought about this a lot over the past few years, and on one hand, figuring out how to use IntelliJ's data analysis abilities is the correct way to fix it, but on the other hand it'll always have it's limitations.

I've considered creating a library that only contains source-only annotations to fix this (and stop encouraging developers to use @SideOnly, which Lex has reprimanded me several times for doing). Feels bad to do something like that for an IntelliJ plugin, but I think it's the best option.