efi_selftest: add tests for QueryVariableInfo at runtime

Since we support QueryVariableInfo at runtime now add the relevant
tests. Since we want those to be reusable at bootime, add them
in a separate file

Add tests for
- Test QueryVariableInfo returns EFI_SUCCESS
- Test null pointers for the function arguments
- Test invalid combination of attributes

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>