runtime-sdk: Add support for consensus staking

[kostko]

Based on #1118

[codecov]

Codecov Report

Merging #1122 (dd60093) into main (733f7ca) will increase coverage by 0.59%.
The diff coverage is 69.29%.

@@            Coverage Diff             @@
##             main    #1122      +/-   ##
==========================================
+ Coverage   55.70%   56.30%   +0.59%     
==========================================
  Files         124      126       +2     
  Lines        8652     8987     +335     
==========================================
+ Hits         4820     5060     +240     
- Misses       3790     3885      +95     
  Partials       42       42              

Impacted Files	Coverage Δ
runtime-sdk/src/dispatcher.rs	13.69% <0.00%> (-0.25%)	⬇️
...untime-sdk/src/modules/consensus_accounts/types.rs	100.00% <ø> (ø)
runtime-sdk/src/modules/rewards/mod.rs	70.42% <18.18%> (-8.69%)	⬇️
runtime-sdk/src/testing/mock.rs	83.72% <20.00%> (-8.39%)	⬇️
runtime-sdk/src/history.rs	44.44% <44.44%> (ø)
runtime-sdk/src/context.rs	69.16% <55.55%> (+0.22%)	⬆️
runtime-sdk/src/modules/accounts/mod.rs	80.56% <60.00%> (-0.33%)	⬇️
runtime-sdk/src/modules/consensus/mod.rs	78.04% <60.00%> (-4.61%)	⬇️
runtime-sdk/src/modules/consensus_accounts/mod.rs	65.99% <68.20%> (+6.59%)	⬆️
...untime-sdk/src/modules/consensus_accounts/state.rs	85.71% <85.71%> (ø)
... and 2 more

... and 1 file with indirect coverage changes

[ptrus]

self TODO: check the main part of the PR, changes in the consensus_accounts module.

[ptrus]

Minor, probably irrelevant? improvement: could start at the height of the smallest cached epoch that is higher than epoch.