test(tvix/eval): add some eval-okay-* tests for trivial types

Change-Id: I85ccc07e08c67abf4fcd3752c58e1702943239ac
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6135
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

tvix/eval/src/tests/tvix_tests/eval-okay-multiple-nested-attrs.exp

@@ -0,0 +1 @@
+{ a = { b = 15; }; b = { c = "test"; }; }