We have various functions to convert to a string, rename them all so we can
count on fmt_X being the formatter for struct X, and make them all return
`char *`.
Sometimes they existed but were private, sometimes they had a
different name. Most take a pointer, but simple types pass by copy:
short_channel_id, amount_msat and amount_sat.
The following public functions changed:
1. psbt_to_b64 -> fmt_wally_psbt.
2. pubkey_to_hexstr -> fmt_pubkey.
3. short_channel_id_to_str -> fmt_short_channel_id (scid by copy now!)
4. fmt_signature -> fmt_secp256k1_ecdsa_signature
5. fmt_amount_sat/fmt_amount_msat pass copy not pointer, return non-const char *.
6. node_id_to_hexstr -> fmt_node_id
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Node ids are pubkeys, but we only use them as pubkeys for routing and checking
gossip messages. So we're packing and unpacking them constantly, and wasting
some space and time.
This introduces a new type, explicitly the SEC1 compressed encoding
(33 bytes). We ensure its validity when we load from the db, or get it
from JSON. We still use 'struct pubkey' for peer messages, which checks
validity.
Results from 5 runs, min-max(mean +/- stddev):
store_load_msec,vsz_kb,store_rewrite_sec,listnodes_sec,listchannels_sec,routing_sec,peer_write_all_sec
39475-39572(39518+/-36),2880732,41.150000-41.390000(41.298+/-0.085),2.260000-2.550000(2.336+/-0.11),44.390000-65.150000(58.648+/-7.5),32.740000-33.020000(32.89+/-0.093),44.130000-45.090000(44.566+/-0.32)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
