provider: has("python3_dynamic") et al. #10980

Vim added more flags for testing yet more dimensions of its Python
situation.  Handle those in eval_has_provider().

vim-patch:8.0.1436: not enough information about what Python version may work
Problem:    Not enough information about what Python version may work.
Solution:   Add "python_compiled", "python3_compiled", "python_dynamic" and
            "python3_dynamic" values for has().

ref: https://github.com/neovim/neovim/pull/10942#issuecomment-529479500

test/functional/provider/python_spec.lua

@@ -37,6 +37,10 @@ end)
 describe('python feature test', function()
   it('works', function()
     eq(1, funcs.has('python'))
+    eq(1, funcs.has('python_compiled'))
+    eq(1, funcs.has('python_dynamic'))
+    eq(0, funcs.has('python_dynamic_'))
+    eq(0, funcs.has('python_'))
   end)
 end)