feature(session): add deadpool-redis compatibility (#381)

* Add compatibility of `deadpool-redis` for the storage `redis_rs`.

* Keep up-to-date the `actix-redis` version.

* Format the project issued by command `cargo +nightly fmt`.

* Add `deadpool-redis` into the documentation and tests.

* Update CHANGES.md.

* Update the documentation of `Deadpool Redis` section on `redis_rs`.

* Replace `no_run` with `ignore` attribute on "Deadpool Redis" example to skip the doc tests failure.

* Rollback the renaming `redis::cmd` to `cmd` for better reading and avoid shadowing, fix the wrong return type on builder function comment.

* Format the project issued by command `cargo +nightly fmt`.

* Format.

* Fix feature naming from the last merge.

* Fix feature missing from the last merge.

* Format the project issued by command `cargo +nightly fmt`.

* Re-import `cookie-session` feature. (Maybe was removed accidentally from the last merge?)

* tmp

* chore: bump deadpool-redis to 0.16

* chore: fixup rest of redis code for pool

* fix: add missing cfg guard

* docs: fix pool docs

---------

Co-authored-by: Rob Ede <robjtede@icloud.com>

actix-session/CHANGES.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Add `redis-session-rustls` crate feature that enables `rustls`-secured Redis sessions.
+- Add `redis-pool` crate feature (off-by-default) which enables `RedisSessionStore::{new, builder}_pooled()` constructors.
 - Rename `redis-rs-session` crate feature to `redis-session`.
 - Rename `redis-rs-tls-session` crate feature to `redis-session-native-tls`.
 - Remove `redis-actor-session` crate feature (and, therefore, the `actix-redis` based storage backend).