bootctl: replace --no-variables by --variables=BOOL

I think the current behaviour of not doing EFI variables when we are run
in a container makes a ton of sense, but in some cases it's useful to
do EFI var setup even when a set of namespaces is set up for us, for
example to recover a hosed installation from a rescue disk.

While we are at it, let's remove some duplicate checks, and
systematically output information why we skip various operations.

Fixes: #36174 #35005

src/bootctl/bootctl.h

@@ -20,7 +20,7 @@ extern char *arg_xbootldr_path;
 extern bool arg_print_esp_path;
 extern bool arg_print_dollar_boot_path;
 extern unsigned arg_print_root_device;
-extern bool arg_touch_variables;
+extern int arg_touch_variables;
 extern bool arg_install_random_seed;
 extern PagerFlags arg_pager_flags;
 extern bool arg_graceful;
@@ -54,3 +54,5 @@ static inline const char* arg_dollar_boot_path(void) {
 
 int acquire_esp(int unprivileged_mode, bool graceful, uint32_t *ret_part, uint64_t *ret_pstart, uint64_t *ret_psize, sd_id128_t *ret_uuid, dev_t *ret_devid);
 int acquire_xbootldr(int unprivileged_mode, sd_id128_t *ret_uuid, dev_t *ret_devid);
+
+bool touch_variables(void);