refactor(map): avoid duplicated khash_t types for values

This reduces the total number of khash_t instantiations from 22 to 8.

Make the khash internal functions take the size of values as a runtime
parameter. This is abstracted with typesafe Map containers which
are still specialized for both key, value type.

Introduce `Set(key)` type for when there is no value.

Refactor shada.c to use Map/Set instead of khash directly.
This requires `map_ref` operation to be more flexible.
Return pointers to both key and value, plus an indicator for new_item.
As a bonus, `map_key` is now redundant.

Instead of Map(cstr_t, FileMarks), use a pointer map as the FileMarks struct is
humongous.

Make `event_strings` actually work like an intern pool instead of wtf it
was doing before.

src/nvim/api/extmark.c

@@ -33,12 +33,10 @@
 void api_extmark_free_all_mem(void)
 {
   String name;
-  handle_T id;
-  map_foreach(&namespace_ids, name, id, {
-    (void)id;
+  map_foreach_key(&namespace_ids, name, {
     xfree(name.data);
   })
-  map_destroy(String, handle_T)(&namespace_ids);
+  map_destroy(String, &namespace_ids);
 }
 
 /// Creates a new namespace or gets an existing one. \*namespace\*
@@ -77,7 +75,7 @@ Dictionary nvim_get_namespaces(void)
   String name;
   handle_T id;
 
-  map_foreach(&namespace_ids, name, id, {
+  map_foreach(handle_T, &namespace_ids, name, id, {
     PUT(retval, name.data, INTEGER_OBJ(id));
   })
 
@@ -88,7 +86,7 @@ const char *describe_ns(NS ns_id)
 {
   String name;
   handle_T id;
-  map_foreach(&namespace_ids, name, id, {
+  map_foreach(handle_T, &namespace_ids, name, id, {
     if ((NS)id == ns_id && name.size) {
       return name.data;
     }

src/nvim/api/extmark.h

@@ -6,7 +6,6 @@
 #include "nvim/decoration.h"
 #include "nvim/macros.h"
 #include "nvim/map.h"
-#include "nvim/map_defs.h"
 #include "nvim/types.h"
 
 EXTERN Map(String, handle_T) namespace_ids INIT(= MAP_INIT);

src/nvim/api/private/helpers.h

@@ -122,13 +122,13 @@
 #define api_free_window(value)
 #define api_free_tabpage(value)
 
-EXTERN PMap(handle_T) buffer_handles INIT(= MAP_INIT);
-EXTERN PMap(handle_T) window_handles INIT(= MAP_INIT);
-EXTERN PMap(handle_T) tabpage_handles INIT(= MAP_INIT);
+EXTERN PMap(int) buffer_handles INIT(= MAP_INIT);
+EXTERN PMap(int) window_handles INIT(= MAP_INIT);
+EXTERN PMap(int) tabpage_handles INIT(= MAP_INIT);
 
-#define handle_get_buffer(h) pmap_get(handle_T)(&buffer_handles, (h))
-#define handle_get_window(h) pmap_get(handle_T)(&window_handles, (h))
-#define handle_get_tabpage(h) pmap_get(handle_T)(&tabpage_handles, (h))
+#define handle_get_buffer(h) pmap_get(int)(&buffer_handles, (h))
+#define handle_get_window(h) pmap_get(int)(&window_handles, (h))
+#define handle_get_tabpage(h) pmap_get(int)(&tabpage_handles, (h))
 
 /// Structure used for saving state for :try
 ///

src/nvim/api/ui.c

@@ -111,7 +111,7 @@ void remote_ui_disconnect(uint64_t channel_id)
   }
   UIData *data = ui->data;
   kv_destroy(data->call_buf);
-  pmap_del(uint64_t)(&connected_uis, channel_id);
+  pmap_del(uint64_t)(&connected_uis, channel_id, NULL);
   ui_detach_impl(ui, channel_id);
 
   // Destroy `ui`.