store cursor-position in snippetString to more accurately restore it.

Cache `static_text` (for insertNodes) and don't query it anew while
luasnip is operating. This is valid under the assumption that all
changes to the buffer are due to luasnip while an api-function (jump,
expand, etc.) is running.

This is enabled by session.luasnip_changedtick
which is set as soon as an api-function is called, and prevents
re-fetching snippetStrings from the buffer (which in turn allows us to
set the cursor-position once, and then have it propagate through all
updates that are triggered subsequently).

This commit also replaces no_region_check_wrap with api_do, which is
more general (handles both jump_active, which prevents recursive
api-calls and luasnip_changedtick)

lua/luasnip/extras/select_choice.lua

@@ -2,14 +2,18 @@ local session = require("luasnip.session")
 local ls = require("luasnip")
 local node_util = require("luasnip.nodes.util")
 
+-- in this procedure, make sure that api_leave is called before
+-- set_choice_callback exits.
 local function set_choice_callback(data)
 	return function(_, indx)
 		if not indx then
+			ls._api_leave()
 			return
 		end
 		-- feed+immediately execute i to enter INSERT after vim.ui.input closes.
 		-- vim.api.nvim_feedkeys("i", "x", false)
-		ls.set_choice(indx, {cursor_restore_data = data})
+		ls._set_choice(indx, {cursor_restore_data = data})
+		ls._api_leave()
 	end
 end
 
@@ -20,7 +24,8 @@ local function select_choice()
 	)
 	local active = session.current_nodes[vim.api.nvim_get_current_buf()]
 
-	local restore_data = node_util.store_cursor_node_relative(active)
+	ls._api_enter()
+	local restore_data = node_util.store_cursor_node_relative(active, {place_cursor_mark = false})
 	vim.ui.select(
 		ls.get_current_choices(),
 		{ kind = "luasnip" },