feat: store witness safety margins on SC

[msgmaxim]

Pull Request

Closes: PRO-983

Checklist

Please conduct a thorough self-review before opening the PR.

• I am confident that the code works.
• I have updated documentation where appropriate.

Summary

As discussed, used storage itmes instead of constants so we can have different values depending on the network. Everything expect for Perseverance is set to 2 blocks (it is 5 blocks on Perseverance as requested in PRO-983)

[linear]

PRO-983 CFE Reads SC Constant for safety margin

We want the safety margin for each chain to be a pallet::constant on the SC, probably in the ingress-egress pallet, such that the CFE can read it to determine the safety margin, and that this can be changed via a runtime upgrade. It also means we can have different margins for different networks rather easily, without having to compile a different engine - as the safety margins are currently stored as engine constants.

1. SC should store a constant for the witnessing safety margin of each chain.
2. CFE needs to read this constant and use it as the safety margin

Out of scope:

• Dynamically adjusting the safety margin while the CFE is running.

The values for these on each public network should be:

Perseverance: 5

Mainnet: 2

(There was a long discussion about this, the tl;dr is that reorgs greater than 2 blocks are very rare on mainnet, and when there is, the chances are that there's a reorg where there's a tx removed entirely is even rarer).

On localnets we can probably bring this down to 2 too - and decrease the ETH margin for localnets while we can too, this should speed up localnets / CI quite a bit.

[kylezs]

This will also need a migration. You can see the state-chain/pallets/cf-ingress-egress/src/migrations/ingress_expiry.rs migration for one way to do this to set different values for the different instances of the instantiable pallets

also note that this PR: #4258 which will probably be merged today, changes the migration process slightly. It doesn't change anything to do with writing the migration file itself along with the pre and post hooks, as in the example above.

[codecov]

Codecov Report

Attention: 26 lines in your changes are missing coverage. Please review.

Comparison is base (e6ad83e) 72% compared to head (4c290bc) 71%.
Report is 10 commits behind head on main.

❗ Current head 4c290bc differs from pull request most recent head d2d3278. Consider uploading reports for the commit d2d3278 to get more accurate results

Files	Patch %	Lines
engine/src/witness/btc.rs	0%	9 Missing ⚠️
engine/src/witness/eth.rs	0%	9 Missing ⚠️
state-chain/node/src/chain_spec.rs	0%	8 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #4260   +/-   ##
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- Coverage     72%     71%   -0%     
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  Files        385     385           
  Lines      63554   63622   +68     
  Branches   63554   63622   +68     
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+ Hits       45448   45479   +31     
- Misses     15749   15797   +48     
+ Partials    2357    2346   -11     

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[msgmaxim]

Added assertions so that the migration can be tested, and checked it with try_runtime_upgrade.ts scirpt. @kylezs