Remove problematic equivocation

[nazar-pc]

Background: https://forum.autonomys.xyz/t/farmer-equivocation-is-problematic/3063?u=nazar-pc

Changes that should be accurately audited are in pallet-subspace's lib.rs and tests.rs. Removal of block list in the runtime changes handling of rewards a bit and I had to update the test and implementation of vote checking to make sure we don't allow farmer to reuse the same solution twice. In particular entries are no longer removed from current block author info and current block voters, instead reward address became optional.

Client-side code still checks equivocation, but doesn't handle it in any meaningful way yet since we do not have a spec for replacement implementation.

Code contributor checklist:

• I have read, understood and followed contributing guide

[teor2345]

Overall this makes sense to me, but I'd like someone else to double-check before it merges.

[nazar-pc]

Adding to merge queue, but would still prefer more eyes on this if possible