Count unknown channel types in anchor reserve

[tankyleo]

    Count unknown channel types in anchor reserve

    Conservatively include channels whose type is not yet known when
    calculating the anchor reserve. Otherwise, opening or accepting new
    channels, or splicing funds into existing channels, can leave too little
    reserved for channels still being negotiated.

    Do not count channels with unknown channel types when assessing whether
    0FC support is required from the chain source. This part is all
    user-controlled, and we do not want to require the chain source to support
    0FC if startup happens with an in-flight channel open, and no other 0FC
    chain source support predicates are true.

    Reported by Project Loupe

Fixes https://github.com/project-loupe/audit-ldk-node/issues/120

[ldk-reviews-bot]

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