[clang] [test] Use %clang_cc1 substitution consistently

Use the `%clang_cc1` substitution consistently across the test suite,
replacing inline `%clang -cc1` invocations, except for one Preprocessor
test where this is causing breakage.  This is necessary to ensure that
additional parameters passed via `%clang` do not interfere with `-cc1`
that must always be passed as the first command-line argument.

Remove the additional substitution blocking `%clang_cc1` use in Driver
tests.  It has been added in 2013 and was supposed to prevent tests
calling `clang -cc1` from being added to Driver.  The state of the test
suite proves that it did not succeed at all.

Differential Revision: https://reviews.llvm.org/D134880