[feature]: Enhance caretaker w/ ability to set user-defined UTXOs and GenesisAmtSats values

[dstadulis]

Is your feature request related to a problem? Please describe.
As a taproot-assets user I want to select user-defined UTXOs and GenesisAmtSats values in order to

• be able to include my taproot-asset proofs in UTXOs I choose
• Reduce inputs / obviate CPFP, in order to update the proofs
• privacy: increase covertness of taproot-asset UTXOs to deny meta-data fingerprinting

[Edit Capturing TODOs from #866]

• Extend tapdb/asset_minting tests to cover new query params for script key, group key, etc.
• Add tests for tapdb/asset_minting/CommitBatchTx, AddSeedlingGroups, FetchSeedlingGroups

taproot-assets/tapgarden/caretaker.go

Lines 53 to 57 in eb79a07

	// GenesisAmtSats is the amount of sats we'll use to anchor created
	// assets within. This value just needs to be greater than dust, as for
	// now, we assume that the tapd client manages asset bearing UTXOs
	// distinctly from normal UTXOs.
	GenesisAmtSats = btcutil.Amount(1_000)

Describe the solution you'd like
tapd and lnd work together to do UTXO selection

Describe alternatives you've considered
recompiling the daemon any time a custom GenesisAmtSats value is desired

[guggero]

Additional requirements concerning PSBT handling during the minting process:

• Ability to spend from custom script UTXO (e.g. genesis input is a 2-of-3 multisig) when minting
  • Requires PSBT interaction to specify inputs with specific signing information
  • When implementing PSBT templating, there should be an option to specify which output the assets should be minted into (which would then use the internal key and BTC amount from the template)
  • Probably requires more RPC steps where the external signing of the PSBT is executed
• Ability to define a custom internal key for the batch (make it independent of the batch public key), to allow specifying a NUMS key for example when the batch sibling is a 2-of-2 multisig.