staking: Add a burn address

[Yawning]

Yet another PR that can rot for months in "don't want to fork the 22.x branch yet" purgatory.

• [x] Define a burn address
• [x] Support burning based off xfers to the burn address
• [x] Test cases
• [ ] Migration

Implements #4755

[codecov[bot]]

Codecov Report

Merging #4756 (050c32d) into master (d8b770b) will increase coverage by 0.10%. The diff coverage is 82.84%.

:exclamation: Current head 050c32d differs from pull request most recent head 07f5399. Consider uploading reports for the commit 07f5399 to get more accurate results

@@            Coverage Diff             @@
##           master    #4756      +/-   ##
==========================================
+ Coverage   66.54%   66.65%   +0.10%     
==========================================
  Files         477      478       +1     
  Lines       51696    51780      +84     
==========================================
+ Hits        34403    34515     +112     
+ Misses      13017    12981      -36     
- Partials     4276     4284       +8     

Impacted Files	Coverage Δ
go/staking/api/api.go	62.72% <ø> (ø)
go/staking/api/sanity_check.go	50.45% <0.00%> (-3.17%)	:arrow_down:
go/common/crypto/signature/signature.go	56.01% <75.00%> (+0.58%)	:arrow_up:
.../consensus/tendermint/apps/staking/transactions.go	73.88% <79.16%> (-0.41%)	:arrow_down:
go/staking/tests/tester.go	92.42% <95.69%> (+0.52%)	:arrow_up:
go/staking/api/address_internal.go	100.00% <100.00%> (ø)
.../worker/compute/executor/committee/transactions.go	79.54% <0.00%> (-6.82%)	:arrow_down:
go/common/cbor/codec.go	78.37% <0.00%> (-5.41%)	:arrow_down:
go/roothash/api/api.go	80.35% <0.00%> (-3.58%)	:arrow_down:
go/sentry/api/grpc.go	40.62% <0.00%> (-3.13%)	:arrow_down:
... and 35 more

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[kostko]

Let's rebase now that master can break consensus.

[Yawning]

I'm not sure what sort of migration is required. The genesis doc sanity check in my branch checks that the burn address is empty.

If someone does happen to use the burn address before this gets deployed I'm not sure what the correct thing to do is, since it is impossible to differentiate between "someone happened to generate the private key" and "someone used the address prematurely".