feat(treesitter): upstream is_parent()

Util from the nvim-treesitter project.
Renamed is_parent to is_ancestor for clarity.

test/functional/treesitter/utils_spec.lua

@@ -0,0 +1,29 @@
+local helpers = require('test.functional.helpers')(after_each)
+
+local clear = helpers.clear
+local insert = helpers.insert
+local eq = helpers.eq
+local exec_lua = helpers.exec_lua
+
+before_each(clear)
+
+describe('treesitter utils', function()
+  clear()
+  it('can find an ancestor', function()
+    insert([[
+      int main() {
+        int x = 3;
+      }]])
+
+    exec_lua([[
+      parser = vim.treesitter.get_parser(0, "c")
+      tree = parser:parse()[1]
+      root = tree:root()
+      ancestor = root:child(0)
+      child = ancestor:child(0)
+    ]])
+
+    eq(true, exec_lua('return vim.treesitter.is_ancestor(ancestor, child)'))
+    eq(false, exec_lua('return vim.treesitter.is_ancestor(child, ancestor)'))
+  end)
+end)