Add a txOut field to our InteractiveTxBuilder.Input interface

[sstone]

This will help us add support for taproot inputs: to create taproot signatures we need all prevouts (and not just prevouts for tx inputs that spend taproot outputs).

[codecov-commenter]

Codecov Report

Merging #2791 (58747b6) into master (e73c1cf) will increase coverage by 0.01%. The diff coverage is 88.88%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2791 +/- ## ========================================== + Coverage 85.83% 85.85% +0.01% ========================================== Files 216 216 Lines 18169 18180 +11 Branches 753 745 -8 ========================================== + Hits 15596 15609 +13 + Misses 2573 2571 -2 ``` | [Files](https://app.codecov.io/gh/ACINQ/eclair/pull/2791?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ACINQ) | Coverage Δ | | |---|---|---| | [...cinq/eclair/channel/fund/InteractiveTxFunder.scala](https://app.codecov.io/gh/ACINQ/eclair/pull/2791?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ACINQ#diff-ZWNsYWlyLWNvcmUvc3JjL21haW4vc2NhbGEvZnIvYWNpbnEvZWNsYWlyL2NoYW5uZWwvZnVuZC9JbnRlcmFjdGl2ZVR4RnVuZGVyLnNjYWxh) | `92.24% <100.00%> (ø)` | | | [...inq/eclair/channel/fund/InteractiveTxBuilder.scala](https://app.codecov.io/gh/ACINQ/eclair/pull/2791?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ACINQ#diff-ZWNsYWlyLWNvcmUvc3JjL21haW4vc2NhbGEvZnIvYWNpbnEvZWNsYWlyL2NoYW5uZWwvZnVuZC9JbnRlcmFjdGl2ZVR4QnVpbGRlci5zY2FsYQ==) | `91.37% <83.33%> (-0.21%)` | :arrow_down: | | [...ire/internal/channel/version4/ChannelCodecs4.scala](https://app.codecov.io/gh/ACINQ/eclair/pull/2791?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ACINQ#diff-ZWNsYWlyLWNvcmUvc3JjL21haW4vc2NhbGEvZnIvYWNpbnEvZWNsYWlyL3dpcmUvaW50ZXJuYWwvY2hhbm5lbC92ZXJzaW9uNC9DaGFubmVsQ29kZWNzNC5zY2FsYQ==) | `99.63% <90.00%> (-0.37%)` | :arrow_down: | ... and [4 files with indirect coverage changes](https://app.codecov.io/gh/ACINQ/eclair/pull/2791/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ACINQ)