Adds a form of spvtest::MakeInstruction which takes two vectors
of operands. That leads to simpler test code.
We can clean up some other test code, in another CL.
Make it a class, since it has non-trivial behaviour for converting
the enumerated value to a uint32_t value. (Comply with style guide.)
Merge EnumCaseWithOperands into EnumCase.
Fixed an issue where some of the tests were testing
the wrong word with the wrong operation. (| != ||).
Coalesced the many versions of EnumCase into one.
Added a get_value() to EnumCase to convert to a uint32_t.
Replaces ASSERT_TRUE(pointer), with ASSERT_NE(nullptr, pointer),
so that we do not do implicit pointer->bool conversion.
Removed const from some test structs since gtest needs to be
able to swap them.
Add text_fixture::TextToBinaryTestBase::CompiledInstructions,
to more easily just examine the generated instructions by skipping
over the header.
Add spvtest::MakeInstruction utility function to easily generate
a vector containing an opcode and its operands.
Use double quotes ("). They can be interspersed with
other whitespace characters, just like shell quoting.
A backslash (\) always escapes the next character.
The end of the stream always terminates the word.
Add AutoText struct to unit test utilities, to easily
make spv_text_t values and reference them as spv_text values.
