go/consensus: Move SubmitEvidence to LightClientBackend

[kostko]

Fixes #3169

This allows light clients to submit evidence of Byzantine behavior.

[codecov]

Codecov Report

Merging #3170 into master will increase coverage by 0.13%.
The diff coverage is 57.50%.

@@            Coverage Diff             @@
##           master    #3170      +/-   ##
==========================================
+ Coverage   68.56%   68.70%   +0.13%     
==========================================
  Files         385      385              
  Lines       37873    37890      +17     
==========================================
+ Hits        25968    26031      +63     
+ Misses       8591     8532      -59     
- Partials     3314     3327      +13     

Impacted Files	Coverage Δ
go/consensus/api/api.go	22.22% <ø> (-15.88%)	⬇️
go/consensus/api/base.go	2.77% <0.00%> (ø)
go/consensus/tendermint/light/client.go	46.34% <0.00%> (-3.23%)	⬇️
go/consensus/tendermint/full/full.go	64.99% <62.50%> (+1.26%)	⬆️
go/consensus/api/grpc.go	69.10% <71.42%> (+1.84%)	⬆️
go/consensus/tendermint/tests/evidence.go	92.72% <100.00%> (+0.57%)	⬆️
go/consensus/tests/tester.go	98.01% <100.00%> (+0.04%)	⬆️
go/worker/common/p2p/error/error.go	71.42% <0.00%> (-28.58%)	⬇️
go/consensus/tendermint/api/errors.go	86.66% <0.00%> (-13.34%)	⬇️
go/storage/metrics.go	78.26% <0.00%> (-6.53%)	⬇️
... and 33 more

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