meson-render-jinja2: use ast.literal_eval()

meson-render-jinja2: use ast.literal_eval()

Imports are sorted in the usual fashion: stdlib first.

literal_eval() parses string/numbers/lists/sets/dicts, and nothing else, while
eval will execute any python code. Using literal_eval() is generally more
correct, because it avoids the risk of side effects from the parsed expression.
In this case, we generate the parsed strings ourselves, so it's very unlikely
to have anything unexpected in the expressions. But let's do the correct thing
anyway.