garbage collect zero-value UTXOs

[darioAnongba]

Garbage collect the residue zero-value UTXOs when creating transactions. Zero-value UTXOs occur when creating tombstones or full burns.
Currently, these UTXOs accumulate in the DB and are never cleaned. This PR introduces a garbage collection mechanism to collect these UTXOs and use them as inputs of transactions initiated by tapd:

• Transfers
• Burns

The PR adds a new swept flag to the managed_utxo table because UTXOs are not removed from the table when spent. This flag is also returned by the ListUtxos RPC endpoint.

The mechanism preserves the liveness and safety properties, ensuring that zero-value UTXOs can never accumulate in the DB. Adding garbage collection to Mint transactions is not necessary to ensure this properties.

Fixes #514

** Note to reviewers**

1. UTXO meaning unspent, keeping the spent outputs in a table called manage_utxos seems like a contradiction, same logic applies for the need of a swept flag in that table. We should either rename the table or store spent utxos somewhere else?
2. Similar to 1. Feels wrong to return the spent UTXOs in the ListUtxos call. Should we rename this to ListOutputs?
3. The pkScript is retrieved by querying the chain_txs table. Is it possible/more efficient to avoid this and somehow recompute it from the data we have?

[coveralls]

Pull Request Test Coverage Report for Build 18382547235

Details

• 21 of 354 (5.93%) changed or added relevant lines in 10 files are covered.
• 28020 unchanged lines in 195 files lost coverage.
• Overall coverage decreased (-15.2%) to 34.469%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tapfreighter/parcel.go	0	4	0.0%
tapdb/sqlc/assets.sql.go	0	6	0.0%
rpcserver.go	0	11	0.0%
tapfreighter/coin_select.go	0	29	0.0%
tapfreighter/chain_porter.go	0	40	0.0%
tapfreighter/wallet.go	0	70	0.0%
tapdb/assets_store.go	3	176	1.7%

Files with Coverage Reduction	New Missed Lines	%
universe/supplyverifier/util.go	1	98.75%
proof/util.go	2	81.63%
tapdb/migrations.go	2	76.19%
address/log.go	3	0.0%
commitment/log.go	3	0.0%
internal/pedersen/commitment.go	3	95.31%
lndservices/log.go	3	0.0%
rfq/log.go	3	0.0%
tapchannel/log.go	3	0.0%
tapdb/supply_syncer.go	3	73.85%

Totals
Change from base Build 18359865357:	-15.2%
Covered Lines:	30524
Relevant Lines:	88554

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💛 - Coveralls