patch 8.2.1480: Vim9: skip expression in search() gives error

Problem:    Vim9: skip expression in search() gives error.
Solution:   use tv_get_bool() eval_expr_to_bool(). (closes #6729)

src/testdir/test_vim9_func.vim

@@ -1379,6 +1379,13 @@ func Test_silent_echo()
   call delete('XTest_silent_echo')
 endfunc
 
+def Test_search()
+  new
+  setline(1, ['foo', 'bar'])
+  let val = 0
+  assert_equal(2, search('bar', 'W', 0, 0, {-> val == 1}))
+enddef
+
 def Fibonacci(n: number): number
   if n < 2
     return n