Improve handling of types and aliases in components (#5591)

This commit fixes more cases from #5565 where `export` items introducing
indices wasn't handled by accident. Additionally this fixes support for
aliasing types from instances which largely wasn't working before. Most
of the fixes here are about correctly maintaining Wasmtime's view of the
type index spaces.

tests/misc_testsuite/component-model/types.wast

@@ -246,3 +246,77 @@
     (type $t101 (list $t100))
   )
   "type nesting is too deep")
+
+(component
+  (type (instance
+    (export $x "x" (instance
+      (type $t u32)
+      (export "y" (type (eq $t)))
+    ))
+    (alias export $x "y" (type $t))
+    (export "my-y" (type (eq $t)))
+  ))
+
+  (type (component
+    (import "x" (instance $x
+      (type $t u32)
+      (export "y" (type (eq $t)))
+    ))
+    (alias export $x "y" (type $t))
+    (export "my-y" (type (eq $t)))
+  ))
+)
+
+(component
+  (type $t u32)
+  (export $t2 "t" (type $t))
+  (type $r (record (field "x" $t2)))
+  (export "r" (type $r))
+)
+
+(component
+  (component
+    (import "x" (instance $i
+      (type $i u32)
+      (export "i" (type (eq $i)))
+    ))
+    (alias export $i "i" (type $i))
+    (export "i" (type $i))
+  )
+)
+
+(component
+  (type $u u32)
+  (instance $i
+    (export "i" (type $u))
+  )
+  (alias export $i "i" (type $i))
+  (export "i" (type $i))
+)
+
+(component
+  (component $c
+    (type $t u32)
+    (export "t" (type $t))
+  )
+  (instance $c (instantiate $c))
+  (export "i" (type $c "t"))
+)
+
+(component
+  (component $c
+    (import "x" (component $c
+      (type $t u32)
+      (export "t" (type (eq $t)))
+    ))
+    (instance $c (instantiate $c))
+    (export "i" (type $c "t"))
+  )
+
+  (component $x
+    (type $t u32)
+    (export "t" (type $t))
+  )
+
+  (instance $c (instantiate $c (with "x" (component $x))))
+)