always accept compressed subgraph responses

[Geal]

• Fix accept compressed subgraph responses by default #2415

Subgraph response decompression was only supported when subgraph request compression was configured, this is now always active

Checklist

Complete the checklist (and note appropriate exceptions) before a final PR is raised.

• Changes are compatible[^1]
• Documentation[^2] completed
• Performance impact assessed and acceptable
• Tests added and passing[^3]
  • Unit Tests
  • Integration Tests
  • Manual Tests

[SimonSapin]

Clippy errors on const ACCEPTED_ENCODINGS: HeaderValue with “a const item should never be interior mutable”. I suspect the mutability in question is the atomic refcounter inside Bytes inside, but it’s never used for a value constructed with from_static:

https://docs.rs/bytes/1.3.0/src/bytes/bytes.rs.html#162-169
https://docs.rs/bytes/1.3.0/src/bytes/bytes.rs.html#872-890

[SimonSapin]

It’s an AtomicPtr but same reasoning: rust-lang/rust-clippy#5812

I think #[allow] is the right thing here.

[Geal]

yes, the allow would make sense