dlopen: take log_level argument and log in fallback stubs

Every dlopen_xxx() helper now takes an int log_level argument. It is
passed through to dlopen_many_sym_or_warn() (which in turn propagates it
to dlopen_verbose() for the library-not-installed case), and is used by
the fallback stub when support for the library is not compiled in to
emit a "<lib> support is not compiled in." message at the caller's level.
Callers pass LOG_DEBUG when gracefully degrading, or a higher level when
the failure should surface, and no longer need to log redundantly at the
call site.

As part of this, dlopen_bpf_full() (which already took a log_level) is
merged into dlopen_bpf() rather than keeping both.

The static inline fallbacks used to live in the headers, which required
pulling log.h in from every header that declared a dlopen_xxx(). Move
them into the .c files instead: the declaration is always outside the
#if HAVE_XXX block, the impl sits outside the outer #if HAVE_XXX wrap
with its own internal #if HAVE_XXX/#else/#endif, and apparmor-util.c,
idn-util.c, libmount-util.c and pam-util.c are now always compiled so
they can host their stubs.

src/test/test-dlopen-so.c

@@ -29,12 +29,12 @@
 #include "tests.h"
 #include "tpm2-util.h"
 
-#define ASSERT_DLOPEN(func, cond)                               \
-        do {                                                    \
-                if (cond)                                       \
-                        ASSERT_OK(func());                      \
-                else                                            \
-                        ASSERT_ERROR(func(), EOPNOTSUPP);       \
+#define ASSERT_DLOPEN(func, cond)                                       \
+        do {                                                            \
+                if (cond)                                               \
+                        ASSERT_OK(func(LOG_DEBUG));                     \
+                else                                                    \
+                        ASSERT_ERROR(func(LOG_DEBUG), EOPNOTSUPP);      \
         } while (false)
 
 static int run(int argc, char **argv) {

src/test/test-execute.c

@@ -1633,7 +1633,7 @@ static int intro(void) {
         if (path_is_read_only_fs("/sys") > 0)
                 return log_tests_skipped("/sys is mounted read-only");
 
-        r = dlopen_libmount();
+        r = dlopen_libmount(LOG_DEBUG);
         if (r < 0)
                 return log_tests_skipped("libmount not available.");
 

src/test/test-kexec.c

@@ -104,7 +104,7 @@ TEST(gzip_round_trip) {
                 gz_path[] = "/tmp/test-kexec-gz.XXXXXX";
         int r;
 
-        r = dlopen_zlib();
+        r = dlopen_zlib(LOG_DEBUG);
         if (r < 0) {
                 log_tests_skipped("zlib not available");
                 return;
@@ -144,7 +144,7 @@ TEST(zboot_synthetic) {
                 zboot_path[] = "/tmp/test-kexec-zboot.XXXXXX";
         int r;
 
-        r = dlopen_zlib();
+        r = dlopen_zlib(LOG_DEBUG);
         if (r < 0) {
                 log_tests_skipped("zlib not available");
                 return;

src/test/test-load-fragment.c

@@ -972,7 +972,7 @@ TEST(config_parse_log_filter_patterns) {
                 TEST_PATTERN("~foobar", 0, 1),
         };
 
-        if (ERRNO_IS_NOT_SUPPORTED(dlopen_pcre2()))
+        if (ERRNO_IS_NOT_SUPPORTED(dlopen_pcre2(LOG_DEBUG)))
                 return (void) log_tests_skipped("PCRE2 support is not available");
 
         FOREACH_ELEMENT(test, regex_tests) {

src/test/test-namespace.c

@@ -213,7 +213,7 @@ TEST(protect_kernel_logs) {
                 return;
         }
 
-        r = dlopen_libmount();
+        r = dlopen_libmount(LOG_DEBUG);
         if (ERRNO_IS_NEG_NOT_SUPPORTED(r)) {
                 (void) log_tests_skipped("libmount support not compiled in");
                 return;

src/test/test-netlink-manual.c

@@ -15,9 +15,9 @@ static int load_module(const char *mod_name) {
         struct kmod_list *l;
         int r;
 
-        r = dlopen_libkmod();
+        r = dlopen_libkmod(LOG_ERR);
         if (r < 0)
-                return log_error_errno(r, "Failed to load libkmod: %m");
+                return r;
 
         ctx = sym_kmod_new(NULL, NULL);
         if (!ctx)