tree-wide: convert dlopen_*() callers to DLOPEN_* wrapper macros

Switch the executable-owned call sites from the plain dlopen_<lib>()
helpers to the new DLOPEN_<LIB>() macros, so that each binary that loads
an optional library at runtime now carries its own .note.dlopen note
instead of relying solely on libsystemd-shared. Each call site passes a
priority reflecting whether it hard-depends on the library (required) or
degrades gracefully without it (recommended).

Co-developed-by: Claude Opus 4.8 <noreply@anthropic.com>

src/sbsign/sbsign.c

@@ -425,7 +425,7 @@ static int verb_sign(int argc, char *argv[], uintptr_t _data, void *userdata) {
         _cleanup_(iovec_done) struct iovec signed_attributes_signature = {};
         int r;
 
-        r = dlopen_libcrypto(LOG_ERR);
+        r = DLOPEN_LIBCRYPTO(LOG_ERR, SD_ELF_NOTE_DLOPEN_PRIORITY_REQUIRED);
         if (r < 0)
                 return r;