send expected epoch along when calling SubmitTx

[matevz]

PR for #1062:

• runtime/client: add expectedEpochNumber parameter to SubmitTx call,
• txnscheduler/committee/node: check whether expectedEpochNumber matches the local one,
• executor/node, merge/node: abort, if state change detected,
• e2e/multiple-runtimes:
  • reduce all group sizes to 1 with no backups,
  • use epochTime mock,
  • add new numComputeWorkers parameter,
• cmd/node/node.go, common/commmittee/node.go, common/worker.go, runtime/client/client.go, worker/common/committee/group.go: access RootHash, Scheduler, Beacon, KeyManager, EpochTime, and Registry fields indirectly using consensus member.

[codecov]

Codecov Report

Merging #2650 into master will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2650      +/-   ##
==========================================
- Coverage   62.90%   62.83%   -0.07%     
==========================================
  Files         370      370              
  Lines       34905    34910       +5     
==========================================
- Hits        21956    21936      -20     
- Misses      10177    10234      +57     
+ Partials     2772     2740      -32     

Impacted Files	Coverage Δ
go/consensus/tendermint/api/api.go	73.58% <0.00%> (-15.10%)	⬇️
go/consensus/api/grpc.go	57.02% <0.00%> (-6.62%)	⬇️
go/worker/common/host/sandboxed.go	70.22% <0.00%> (-5.14%)	⬇️
.../consensus/tendermint/apps/epochtime_mock/state.go	84.61% <0.00%> (-5.13%)	⬇️
go/oasis-node/cmd/debug/byzantine/byzantine.go	35.01% <0.00%> (-5.04%)	⬇️
...o/consensus/tendermint/apps/scheduler/scheduler.go	71.70% <0.00%> (-3.03%)	⬇️
go/oasis-node/cmd/debug/byzantine/merge.go	74.68% <0.00%> (-2.54%)	⬇️
go/worker/common/p2p/p2p.go	66.21% <0.00%> (-1.36%)	⬇️
go/storage/client/client.go	73.47% <0.00%> (-0.87%)	⬇️
go/worker/registration/worker.go	66.66% <0.00%> (-0.50%)	⬇️
... and 19 more

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[kostko]

Mostly looks good, some nits.