perf: state root cache for slot n+1

[rodrigo-o]

Description

This PR solves an issue where we calculated the state and block root twice, once at the end of an slot and at the beginning of the following due to a lack of access to the whole state info.

The solution was to pass the whole state info (instead of the beacon state) and set a new previous_roots map which allowed us to avoid the recalculation when any of the roots was already calculated.

[rodrigo-o]

The block processing has reduced its time by ~3/4 seconds

Before

INFO 19:30:26.903 [Fork choice] Adding new block slot=10997406 root=0x172..b1a8
INFO 19:30:42.722 [Fork choice] Block processed. Recomputing head. 
INFO 19:30:43.274 [Fork choice] Added new block slot=10997406 root=0x172..b1a8
INFO 19:30:43.274 [Fork choice] Recomputed head slot=10997406 root=0x172..b1a8
INFO 19:30:43.274 [Fork choice] Block processing time: 15.819s | Recompute head time: 0.176s 

INFO 19:30:43.276 [Fork choice] Adding new block slot=10997407 root=0xe95..672d
INFO 19:30:59.552 [Fork choice] Block processed. Recomputing head. 
INFO 19:31:00.352 [Fork choice] Added new block slot=10997407 root=0xe95..672d
INFO 19:31:00.353 [Fork choice] Recomputed head slot=10997407 root=0xe95..672d
INFO 19:31:00.353 [Fork choice] Block processing time: 16.276s | Recompute head time: 0.288s

After

INFO 18:22:35.125 [Fork choice] Adding new block slot=11011512 root=0x0b8..3c58
INFO 18:22:47.930 [Fork choice] Block processed. Recomputing head. 
INFO 18:22:48.380 [Fork choice] Added new block slot=11011512 root=0x0b8..3c58
INFO 18:22:48.380 [Fork choice] Recomputed head slot=11011512 root=0x0b8..3c58
INFO 18:22:48.380 [Fork choice] Block processing time: 12.805 s | Head recompute time: 0.451 s 

INFO 18:22:48.382 [Fork choice] Adding new block slot=11011513 root=0xfed..6abf
INFO 18:22:59.945 [Fork choice] Block processed. Recomputing head. 
INFO 18:23:00.447 [Fork choice] Added new block slot=11011513 root=0xfed..6abf
INFO 18:23:00.447 [Fork choice] Recomputed head slot=11011513 root=0xfed..6abf
INFO 18:23:00.447 [Fork choice] Block processing time: 11.563 s | Head recompute time: 0.502 s 

[ElFantasma]

Added telemetry instrumentation for process_slot function to improve Grafana precision in fork choice handler times chart:
Now we can measure this PR impact on charts:
Before:

After:

[ElFantasma]

Nice 👍