Remove the option to manually set a fee rate for opening channels

[JssDWt]

Is your feature request related to a problem? Please describe.
Users like to open channels with cheap rates. But they don't know what they're doing. What often happens is they open a channel with a fee rate that is too low and the channel will not open within two weeks, causing the peer to forget about the channel. That could in some cases lead to loss of funds.

Describe the solution you'd like
Remove the option to manually set a fee rate in RTL. Or at least hide it in some advanced section with a clear warning that you have to know what you're doing. The days of 1 sat/vbyte are over.

Describe alternatives you've considered

Additional context

[saubyk]

With the current design, the user will have to click on Advanced Options and then select Fee and then enter the rate manually. If the user doesn't go to the advanced option, default rate is selected by the underlying implementation like LND or Core Lightning. Obfuscating this option further will degrade the UX significantly.

Instead we can add a warning which says something like:
You have chosen a low fee rate, which reduces the chances of this transaction being mined and may also lead to loss of funds

To make the feature even better, a lookup for the prevailing fee rate can be added via the mempool.space api. The response from the fee rate can be compared with the fee rate user has entered and if the user entered fee rate is lower than the low priority rate, the above mentioned warning should be shown to the user.