chore(dependencies): reduce default dependencies

[tottoto]

httpdate and want are used in some combinations of features. Although Cargo does not provide such a combined features configuration, the scopes could be reduced.

[seanmonstar]

Thanks!

(Now I wonder, is there a CI job we could setup to catch these?)

[tottoto]

cargo-udeps can handle feature aware checking. For hyper's default and full feature, it can be checked with cargo-udeps (like tonic project, in this ci, tonic checks each feature with cargo-hack). Regarding the another features, as hyper uses some crates in the combination of multiple feature, it seem not to be able to achieve minimal dependencies for any possible features combination.

[tottoto]

Opend #3334 to check unused dependencies.