kunit: eliminate KUNIT_INIT_*_ASSERT_STRUCT macros

These macros exist because passing an initializer list to other macros
is hard.

The goal of these macros is to generate a line like
  struct $ASSERT_TYPE __assertion = $APPROPRIATE_INITIALIZER;
e.g.
  struct kunit_unary_assertion __assertion = {
	  .condition = "foo()",
	  .expected_true = true
  };

But the challenge is you can't pass `{.condition=..., .expect_true=...}`
as a macro argument, since the comma means you're actually passing two
arguments, `{.condition=...` and `.expect_true=....}`.
So we'd made custom macros for each different initializer-list shape.

But we can work around this with the following generic macro
  #define KUNIT_INIT_ASSERT(initializers...) { initializers }

Note: this has the downside that we have to rename some macros arguments
to not conflict with the struct field names (e.g. `expected_true`).
It's a bit gross, but probably worth reducing the # of macros.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>