tree-wide: use 'Architecture' type consistently across the tree

Some parts of our tree used 'Architecture' for storing architectures,
others used ints. Let's unify on the former.

Inspired by #22952's rework of the 'Virtualization' enum.

src/shared/condition.c

@@ -490,7 +490,7 @@ static int condition_test_virtualization(Condition *c, char **env) {
 }
 
 static int condition_test_architecture(Condition *c, char **env) {
-        int a, b;
+        Architecture a, b;
 
         assert(c);
         assert(c->parameter);

src/shared/dissect-image.c

@@ -612,7 +612,7 @@ static void dissected_partition_done(DissectedPartition *p) {
 
         *p = (DissectedPartition) {
                 .partno = -1,
-                .architecture = -1
+                .architecture = _ARCHITECTURE_INVALID,
         };
 }
 
@@ -917,7 +917,7 @@ int dissect_image(
 
                 if (is_gpt) {
                         PartitionDesignator designator = _PARTITION_DESIGNATOR_INVALID;
-                        int architecture = _ARCHITECTURE_INVALID;
+                        Architecture architecture = _ARCHITECTURE_INVALID;
                         const char *stype, *sid, *fstype = NULL, *label;
                         sd_id128_t type_id, id;
                         bool rw = true, growfs = false;

src/shared/dissect-image.h

@@ -20,9 +20,9 @@ struct DissectedPartition {
         bool found:1;
         bool rw:1;
         bool growfs:1;
-        int partno;        /* -1 if there was no partition and the images contains a file system directly */
-        int architecture;  /* Intended architecture: either native, secondary or unset (-1). */
-        sd_id128_t uuid;   /* Partition entry UUID as reported by the GPT */
+        int partno;                 /* -1 if there was no partition and the images contains a file system directly */
+        Architecture architecture;  /* Intended architecture: either native, secondary or unset ARCHITECTURE_INVALID. */
+        sd_id128_t uuid;            /* Partition entry UUID as reported by the GPT */
         char *fstype;
         char *node;
         char *label;