cutils: Adjust signature of parse_uint[_full]

It's already confusing that we have two very similar functions for
wrapping the parse of a 64-bit unsigned value, differing mainly on
whether they permit leading '-'.  Adjust the signature of parse_uint()
and parse_uint_full() to be like all of qemu_strto*(): put the result
parameter last, use the same types (uint64_t and unsigned long long
have the same width, but are not always the same type), and mark
endptr const (this latter change only affects the rare caller of
parse_uint).  Adjust all callers in the tree.

While at it, note that since cutils.c already includes:

    QEMU_BUILD_BUG_ON(sizeof(int64_t) != sizeof(long long));

we are guaranteed that the result of parse_uint* cannot exceed
UINT64_MAX (or the build would have failed), so we can drop
pre-existing dead comparisons in opts-visitor.c that were never false.

Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20230522190441.64278-8-eblake@redhat.com>
[eblake: Drop dead code spotted by Markus]
Signed-off-by: Eric Blake <eblake@redhat.com>

audio/audio_legacy.c

@@ -35,8 +35,8 @@
 
 static uint32_t toui32(const char *str)
 {
-    unsigned long long ret;
-    if (parse_uint_full(str, &ret, 10) || ret > UINT32_MAX) {
+    uint64_t ret;
+    if (parse_uint_full(str, 10, &ret) || ret > UINT32_MAX) {
         dolog("Invalid integer value `%s'\n", str);
         exit(1);
     }