Change PubKey/PrivKey prefixes of "ostracon/" to "tendermint/" for compatibility (#445)

[torao]

Description

This PR changes the name of public and private key prefixes ostracon/ to tendermint/ for compatibility with Cosmos assets.

1. The private key may remain "ostracon/PrivKeyXxx" since it's never exposed to the outside world. However, it makes no sense to keep the ostracon prefix until the key pair names are asymmetric, so it's modified with "tendermint/PrivKeyXxx"
2. BLS12 and Composite key types are not compatible rather than current Cosmos assets to begin with. To make this clear, these Ostracon-specific prefixes are left as "ostracon/". If the Cosmos assets will support the Ostracon specification, they would adopt the ostracon/ prefix :)

Closes: #445

[codecov]

Codecov Report

Merging #447 (4eb4729) into main (f42887f) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #447      +/-   ##
==========================================
+ Coverage   65.48%   65.51%   +0.03%     
==========================================
  Files         278      278              
  Lines       37926    37926              
==========================================
+ Hits        24834    24847      +13     
+ Misses      11284    11270      -14     
- Partials     1808     1809       +1     

Impacted Files	Coverage Δ
config/toml.go	74.19% <ø> (ø)
crypto/ed25519/ed25519.go	46.34% <ø> (ø)
crypto/secp256k1/secp256k1.go	69.56% <ø> (ø)
crypto/sr25519/encoding.go	100.00% <ø> (ø)
privval/signer_server.go	89.28% <0.00%> (-5.36%)	⬇️
statesync/snapshots.go	93.71% <0.00%> (-1.26%)	⬇️
consensus/reactor.go	74.57% <0.00%> (-0.98%)	⬇️
p2p/pex/pex_reactor.go	80.28% <0.00%> (-0.62%)	⬇️
proxy/multi_app_conn.go	47.66% <0.00%> (ø)
consensus/state.go	73.85% <0.00%> (+0.11%)	⬆️
... and 5 more