Allow to pass min_cltv_expiry_delta for hold invoices

[frnandu]

Should we break receive_for_hash method signature by adding it at the end, or rather add new methods like
receive_for_hash_with_min_cltv(...) and receive_variable_amount_for_hash_with_min_cltv(...) ?

[frnandu]

@rolznz wdyt?

[rolznz]

@frnandu adding new methods seems more inline with what upstream might add, but either is fine