Caches of outside APIs live in /var/cache/sww (closes #314)

The answers of GeoJS, the lists fetched by URL, the DNS blocklists,
AbuseIPDB and routewatch each go in a cache file in SWW_CACHE_DIR
(default /var/cache/sww): lookups.json, lists.json, dnsbl.json,
abuseipdb-scores.json and routewatch.json. reputation.json is gone. The
AbuseIPDB checks spent today are a count, not a cache, and stay in
SWW_STATE_DIR as abuseipdb-checks-spent.json.

A cache file never stops the start: one that does not parse is set
aside as an edit is, one that cannot be read is written over, and its
cache starts empty. An unwritable SWW_CACHE_DIR stops the start, as an
unwritable SWW_STATE_DIR does. Each directory is watched on its own.
The run script makes the cache directory and gives it to sww.

Model: opus-5-5

internal/sww/waf_test.go

@@ -67,6 +67,7 @@ func TestMainRunsWAF(t *testing.T) {
 		commandForMain+"="+wafCommand,
 		listenAddr+"="+localhost+":0",
 		stateDir+"="+dir,
+		cacheDir+"="+dir,
 		rulesDir+"="+t.TempDir(),
 		lookupSource+"=off")