## Issue Addressed
N/A
## Proposed Changes
Add lints for rust 1.71
[3789134](3789134ae2) is probably the one that needs most attention as it changes beacon state code. I changed the `is_in_inactivity_leak ` function to return a `ArithError` as not all consumers of that function work well with a `BeaconState::Error`.
## Issue Addressed
Closes#4354Closes#3987
Replaces #4305, #4283
## Proposed Changes
This switches the default slasher backend _back_ to LMDB.
If an MDBX database exists and the MDBX backend is enabled then MDBX will continue to be used. Our release binaries and Docker images will continue to include MDBX for as long as it is practical, so users of these should not notice any difference.
The main benefit is to users compiling from source and devs running tests. These users no longer have to struggle to compile MDBX and deal with the compatibility issues that arises. Similarly, devs don't need to worry about toggling feature flags in tests or risk forgetting to run the slasher tests due to backend issues.
