Add a decompression API and improve configuration of gateway

[freya022]

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Changes

• Internal code
• Library interface (affecting end-user code)
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Description

This PR creates a new API to decompress gateway messages, which external libraries can hook into.

At the time of writing, the only library using this is discord-zstd-java.

Supersedes #2982

Changes

Both JDABuilder and DefaultShardManagerBuilder had their setMaxBufferSize, setCompression and setGatewayEncoding deprecated. They are now configured with setGatewayConfig and setGatewayConfigProvider.

New features

Decompression using InputStream was added and is configurable in GatewayConfig

• This is opt-in and allows even higher efficiency at the cost of no JSON being logged in case of decompression/decoding errors
• Currently, this mode does not allow using the ETF encoding.