RFC: simplifications and suggestions on open/accept limits.

The message discusses problems encountered in the protocol where agreement on values has not been reached, leading to defacto generally-accepted values that are not in the specification. It proposes suggestions to re-examine these values based on experience and simplify or refine them. Specifically, it addresses different variables such as funding_satoshis, dust_limit_satoshis, max_htlc_value_in_flight_msat, channel_reserve_satoshis, and minimum_depth, providing current values accepted by c-lightning, Eclair, and lnd. The message suggests improvements for each of these variables based on their current values and the proposed changes suggest that any channel under 3 x min(our_dust_limit, their_dust_limit) should be rejected and the variable dust_limit_satoshis should be made customizable in the future. Additionally, the suggestion is made to drop max_htlc_value_in_flight_msat and to revise the value for channel_reserve_satoshis to 483. Finally, it proposes that the minimum_depth value should be increased to 6.