Cache downloads for MCP functions.

[LexManos]

In Forge dev, we setup MCP three times, Client/Server/Joined. Each has a download task. downloadClient downloadServer And Joined downloads both.

The downloaded files are cached in the mcp folder for that specific side. Causing it to download the client and server twice.

This also effects setting up a differtn MCP version, for the same MC version.

We need to setup some form of higher level cache for use in these functions. Just to save downloading.

https://github.com/MinecraftForge/ForgeGradle/blob/097dd2a7145a3a4384ffa77876a55fe0b46b6551/src/mcp/java/net/minecraftforge/gradle/mcp/function/AbstractDownloadMCFunction.java