Redb slasher backend impl (#4529)

* initial redb impl

* redb impl

* remove phantom data

* fixed table definition

* fighting the borrow checker

* a rough draft that doesnt cause lifetime issues

* refactoring

* refactor

* refactor

* passing unit tests

* refactor

* refactor

* refactor

* commit

* move everything to one database

* remove panics, ready for a review

* merge

* a working redb impl

* passing a ref of txn to cursor

* this tries to create a second write transaction when initializing cursor. breaks everything

* Use 2 lifetimes and subtyping

Also fixes a bug in last_key caused by rev and next_back cancelling out

* Move table into cursor

* Merge remote-tracking branch 'origin/unstable' into redb-slasher-backend-impl

* changes based on feedback

* update lmdb

* fix lifetime issues

* moving everything from Cursor to Transaction

* update

* upgrade to redb 2.0

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into redb-slasher-backend-impl

* bring back cursor

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into redb-slasher-backend-impl

* fix delete while

* linting

* linting

* switch to lmdb

* update redb to v2.1

* build fixes, remove unwrap or default

* another build error

* hopefully this is the last build error

* fmt

* cargo.toml

* fix mdbx

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into redb-slasher-backend-impl

* Remove a collect

* Merge remote-tracking branch 'origin/unstable' into redb-slasher-backend-impl

* Merge branch 'redb-slasher-backend-impl' of https://github.com/eserilev/lighthouse into redb-slasher-backend-impl

* re-enable test

* fix failing slasher test

* Merge remote-tracking branch 'origin/unstable' into redb-slasher-backend-impl

* Rename DB file to `slasher.redb`

Makefile

@@ -15,7 +15,7 @@ PINNED_NIGHTLY ?= nightly
 CLIPPY_PINNED_NIGHTLY=nightly-2022-05-19
 
 # List of features to use when cross-compiling. Can be overridden via the environment.
-CROSS_FEATURES ?= gnosis,slasher-lmdb,slasher-mdbx,jemalloc
+CROSS_FEATURES ?= gnosis,slasher-lmdb,slasher-mdbx,slasher-redb,jemalloc
 
 # Cargo profile for Cross builds. Default is for local builds, CI uses an override.
 CROSS_PROFILE ?= release