staking: Add missing events

[abukosek]

When testing the backported staking events for 20.6.1, kostko found a few events that I missed, so I added them in this PR.

[codecov]

Codecov Report

Merging #2935 into master will decrease coverage by 0.14%.
The diff coverage is 48.83%.

@@            Coverage Diff             @@
##           master    #2935      +/-   ##
==========================================
- Coverage   68.57%   68.42%   -0.15%     
==========================================
  Files         361      361              
  Lines       35086    35123      +37     
==========================================
- Hits        24060    24034      -26     
- Misses       7945     7998      +53     
- Partials     3081     3091      +10     

Impacted Files	Coverage Δ
go/staking/api/sanity_check.go	49.15% <0.00%> (-0.85%)	⬇️
go/consensus/tendermint/apps/staking/query.go	49.09% <14.28%> (-22.34%)	⬇️
...o/consensus/tendermint/apps/staking/state/state.go	58.64% <85.71%> (+0.36%)	⬆️
go/consensus/tendermint/abci/mux.go	69.81% <100.00%> (-0.17%)	⬇️
go/consensus/tendermint/apps/staking/fees.go	45.98% <100.00%> (-1.46%)	⬇️
go/oasis-node/cmd/common/metrics/disk.go	65.51% <0.00%> (-20.69%)	⬇️
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%)	⬇️
go/oasis-node/cmd/common/metrics/resource.go	84.00% <0.00%> (-8.00%)	⬇️
.../consensus/tendermint/apps/roothash/state/state.go	68.62% <0.00%> (-3.93%)	⬇️
... and 31 more

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