Allow rotating a subset of collators instead of all of them

[tmpolaczyk]

Adds new field to pallet_configuration: full_rotation_mode. Allows to specify how to perform the rotation, allowing a different value for each kind of chain (orchestrator, parachain, parathread):

• Default: RotateAll, will rotate all collators (as before this PR)
• KeepAll (same as disabling rotation, but now can be set only for parathreads or only for orchestrator for example)
• KeepCollators: will keep N collators assigned on every rotation. If the collators are still eligible, this guarantees there will be N collators that don't rotate.
• KeepPerbill: same but allows to easily set it to 50%, allowing to change the number of collators per chain without having to also update this value. This refers to the % respect to the max number of collators, so if max_orchestrator = 5 but there are only 2 collators assigned to the orchestrator chain, and we try to keep 50%, then it will try to keep 2.5 collators, so all of them.

Contains migration for configuration pallet. I had to fix the migration because it used a hardcoded key that depends on pallet name, thus failing in dancelight.

[github-actions]

WASM runtime size check:

Compared to target branch

dancebox runtime: 1416 KB (no changes) ✅

flashbox runtime: 824 KB (no changes) ✅

dancelight runtime: 2144 KB (no changes) ✅

container chain template simple runtime: 1124 KB (no changes) ✅

container chain template frontier runtime: 1400 KB (no changes) ✅

[github-actions]

Coverage Report

(master)

@@                   Coverage Diff                    @@
##           master   tomasz-rotate-subset      +/-   ##
========================================================
+ Coverage   65.15%                 65.27%   +0.12%     
+ Files         327                    329       +2     
+ Lines       57299                  57620     +321     
========================================================
+ Hits        37330                  37608     +278     
+ Misses      19969                  20012      +43     

Files Changed	Coverage
/node/src/chain_spec/dancebox.rs	94.92% (+0.04%)	✅
/node/src/chain_spec/flashbox.rs	70.66% (-0.16%)	❗
/node/src/rpc.rs	96.43% (-1.44%)	❗
/node/src/service.rs	15.54% (+2.93%)	✅
/pallets/collator-assignment/src/assignment.rs	99.33% (+0.04%)	✅
/pallets/collator-assignment/src/lib.rs	98.69% (+1.04%)	✅
/pallets/configuration/src/lib.rs	86.43% (+2.78%)	✅
/primitives/traits/src/lib.rs	62.94% (+1.34%)	✅
/runtime/common/src/migrations.rs	86.23% (-4.09%)	❗
/runtime/dancebox/src/tests/integration_test.rs	99.70% (-0.01%)	❗

Coverage generated Fri Dec 20 14:55:15 UTC 2024

[chexware]

Besides the unresolved conversations all looks good to me

[girazoki]

in general I think it looks good, just a few nitpicks from open conversations!