Feat: split compression features for Gzip and Brotli support

[BastiDood]

Hello there! This PR splits the compression feature into two: compression-brotli (Brotli) and compression-gzip (Deflate and Gzip). As their names suggest, each feature is responsible for enabling support for their respective compression algorithms.

This is done in an effort to minimize the cargo tree for those who do not intend to use one or the other. Allowing the warp consumer to choose which compression algorithms to support gives finer-grained control over their dependencies, which is nice!

The async-compression crate pulls in the brotli crate when that feature is enabled. Similarly, it pulls in the flate2 crate when the deflate feature or the gzip feature is enabled. Observe that the deflate and gzip features have been merged as the compression-gzip feature in warp since they both indirectly pull in the flate2 crate anyway.

In order to maintain backwards-compatibility, the compression feature is now set to enable both compression-brotli and compression-gzip, which is the current behavior prior to this change.

To that end, if there are any issues with this PR, I'd be glad to resolve them. Thanks! 🎉

[seanmonstar]

This looks excellent, thank you!

I have another PR running through CI which I think will cause a conflict with this one, so you may need to update in a few...

[BastiDood]

Alrighty, everything seems to be ready! I have rebased the changes onto the latest master to keep the Git history clean. 🚀