lncli: Allow lncli to read binary PSBTs from a file

[antonilol]

BIP 174 states that PSBTs can be encoded in 2 formats:

• plain text as base64
• in a file as binary

With this change, lncli will also try to read a PSBT as binary

Change Description

Description of change / link to associated issue.

closes #7119

Read PSBT/hex transaction based on the prefix, which is different for every of the 3:

• binary psbt: "psbt\xff"
• base64 psbt: "cHNidP"
• hex tx: at least 2 hex chars, none of the above do

Steps to Test

Steps for reviewers to follow to test the change.

lncli openchannel <pubkey> <amount> --psbt

the first input box (funded psbt) allows to enter:

• a base64 psbt
• file path to a base64 psbt
• file path to a binary psbt (new)

the second input box (signed psbt/tx) also allows the above 3, and hex encoded transactions

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[guggero]

tACK, very nice!

One small thing that we could also update now is the message in the CLI that now shows (or path to text file): , that could just be or path to file):

[antonilol]

One small thing that we could also update now is the message in the CLI that now shows (or path to text file): , that could just be or path to file):

makes sense, changed it

[guggero]

Needs a rebase, then this is good to go.