Add pool gap capability

[paweljakubas]

Context

Various resources being children of accXPrv play role in cardano blockchain. It would be good to be able to generate all possible keys that can participate at a given moment:

• stake credential
• payment credentials which set is ruled by pool gap and the latest used index - here both external and internal ones (changes)
• policy keys used in asset minting
  Having that one could easily produce resources to be observed in a given moment. It could be useful building block of wallet, should nicely compose with kupo, etc.

Decision

Let's create proper functionality in core and expose it in command line:

cat acct.xsk | cardano-address key set --poolgap 20 --used 1 --all 
cat acct.xsk | cardano-address key set --poolgap 20 --number 1  --stake
cat acct.xsk | cardano-address key set --poolgap 20 --used 11 --external
cat acct.xsk | cardano-address key set --poolgap 20 --used 12 --internal
cat acct.xsk | cardano-address key set --poolgap 20 --number 1 --policy --stake
cat acct.xsk | cardano-address key set --poolgap 20 --number 100 --all     //100 external, 100 internal, 1 policy, 1 stake

There should be optional also to determine if it is signing or verification key.

Acceptance Criteria

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Development

QA