ww: lib tests run via -T test mode; bare mains retired (closes @test conversion)

'ww test' gains the istest build path (-T injection in build_one/
buildone) and do_test/dotest accept -I, mirroring do_run - both twins.
The 35 converted lib tests drop their interim bare mains (-T
synthesizes the entry from @test fns and rejects a user main); their
35 C run-drivers flip 'ww run' -> 'ww test'; 989_lib_byteid compiles
lib tests under -T (8 user-main probe fixtures stay non-T, gated on
the fixture field). Abort-on-first-failure stands until the deferred
record-and-continue harness lands with the multi-package arc.

lib/hash/crc32/crc32_test.ww

@@ -52,13 +52,3 @@ fn check(s: str, ieee: u32, cast: u32, koop: u32) void = {
 	check("GNU's not UNIX",
 		224734747u32, 200511816u32, 332335539u32);
 };
-
-export fn main() i32 = {
-	vec_empty();
-	vec_fire();
-	vec_setfire();
-	vec_blm();
-	vec_unix();
-	vec_gnu();
-	return 0;
-};