[bug]: lnd should NOT accept psbts with sub 1 sat/vb

[feelancer21]

Pre-Submission Checklist

• I have searched the existing issues and believe this is a new bug.
• I am not asking a question about how to use lnd, but reporting a bug (otherwise open a discussion).

LND Version

see #10260

LND Configuration

see #10260

Backend Version

see #10260

Backend Configuration

see #10260

OS/Distribution

see #10260

Bug Details & Steps to Reproduce

1. As described here([bug]: lnd does not send psbts with sub 1sat/vb to bitcoin core #10260), lnd accepts psbt via RPC (sent by bos open) and opens the channels. However, since sub 1 sat/vb is not supported by lnd ([feature]: Allow transactions with a lower fee rate than 1 sat/vbyte #10169), such psbts should be validated and rejected directly upon receipt via RPC.

2. Furthermore, the currently logged error message is incorrect.

Expected Behavior

1. lnd should directly reject psbts received via RPC with sub 1 sat/vb.
2. lnd should return a correct error message via RPC and write it to the log.

Debug Information

see #10260

Environment

see #10260

[rdmxq]

Or LND should just support sub 1s/vb txs, much better. Then there's the privcy factor, if everyone is using sub1s/vb then LND does not support it, LND onchain transactions become much more identifiable.