runtime: Cleanup some runtime host protocol messages

[kostko]

Noticed while writing docs in #3054.

The major change is removing state root parameters from RPC messages as these are unused and don't make sense.

[codecov]

Codecov Report

Merging #3055 into master will decrease coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3055      +/-   ##
==========================================
- Coverage   68.47%   68.24%   -0.24%     
==========================================
  Files         372      372              
  Lines       36444    36441       -3     
==========================================
- Hits        24955    24869      -86     
- Misses       8294     8362      +68     
- Partials     3195     3210      +15     

Impacted Files	Coverage Δ
go/common/version/version.go	84.00% <ø> (ø)
go/runtime/host/protocol/types.go	50.00% <ø> (ø)
go/worker/keymanager/init.go	69.56% <ø> (-0.65%)	⬇️
go/worker/keymanager/worker.go	67.16% <100.00%> (-0.20%)	⬇️
go/consensus/tendermint/api/errors.go	86.66% <0.00%> (-13.34%)	⬇️
go/consensus/tendermint/api/api.go	79.41% <0.00%> (-11.77%)	⬇️
go/worker/compute/executor/committee/state.go	74.07% <0.00%> (-11.12%)	⬇️
go/consensus/tendermint/apps/roothash/query.go	68.42% <0.00%> (-10.53%)	⬇️
...ompute/txnscheduler/algorithm/batching/batching.go	78.66% <0.00%> (-6.67%)	⬇️
go/storage/metrics.go	71.73% <0.00%> (-6.53%)	⬇️
... and 24 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 925b7f2...1e0d475. Read the comment docs.