go/consensus/tendermint/apps: Avoid loading all registered runtimes

[kostko]

Based on #2504
Fixes #2538

This is a performance optimization to avoid loading a list of all registered
runtimes into memory in cases when only a specific runtime is actually needed.

[codecov]

Codecov Report

Merging #2544 into master will decrease coverage by 0.07%.
The diff coverage is 57.33%.

@@            Coverage Diff             @@
##           master    #2544      +/-   ##
==========================================
- Coverage   67.17%   67.09%   -0.08%     
==========================================
  Files         330      330              
  Lines       30577    30562      -15     
==========================================
- Hits        20539    20506      -33     
- Misses       7482     7498      +16     
- Partials     2556     2558       +2

Impacted Files	Coverage Δ
...consensus/tendermint/apps/keymanager/keymanager.go	61.48% <100%> (ø)	⬆️
...consensus/tendermint/apps/registry/transactions.go	44.27% <100%> (+1.54%)	⬆️
go/registry/api/api.go	39.43% <50%> (+0.14%)	⬆️
go/keymanager/api/api.go	68.96% <50%> (ø)	⬆️
go/worker/keymanager/service.go	55.55% <0%> (-22.23%)	⬇️
go/storage/mkvs/urkel/writelog/iterator.go	76.36% <0%> (-16.37%)	⬇️
go/worker/compute/committee/state.go	74.07% <0%> (-11.12%)	⬇️
go/worker/compute/committee/node.go	61.97% <0%> (-4.63%)	⬇️
go/storage/api/root_cache.go	70.11% <0%> (-4.6%)	⬇️
go/consensus/tendermint/apps/registry/query.go	68.75% <0%> (-4.17%)	⬇️
... and 22 more

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