libstdthreads: Move to the runtime package

This library is required for C11 conformance, and is tiny (11kB), so
instead of creating a bunch of packages for it, put it in runtime.

Although this is a core C library and might be expected to live in
clibs, kib objected to this on the basis that almost nothing actually
uses libstdthreads and putting it in clibs would be wasteful.

MFC after:	1 day
Reviewed by:	kib
Sponsored by:	https://www.patreon.com/bsdivy
Differential Revision:	https://reviews.freebsd.org/D52792

lib/libstdthreads/Makefile

@@ -1,4 +1,4 @@
-PACKAGE=lib${LIB}
+PACKAGE=runtime
 LIB=	stdthreads
 SHLIB_MAJOR= 0
 

release/packages/ucl/libstdthreads-all.ucl

@@ -1,28 +0,0 @@
-/*
- * SPDX-License-Identifier: ISC
- *
- * Copyright (c) 2025 Lexi Winter <ivy@FreeBSD.org>
- *
- * Permission to use, copy, modify, and distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
- * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
- * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
- * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
- */
-
-comment = "C11 threading library"
-
-desc = <<EOD
-libstdthreads provides the thread-control interface defined in the
-ISO/IEC 9899:2011 (C11) standard.
-EOD
-
-annotations {
-	set = "optional,optional-jail"
-}