[SYCL RTC] Introduce --auto-pch support

[aelovikov-intel]

Compilation of #include <sycl/sycl.hpp> is slow and that's especially problematic for SYCL RTC (run-time compilation). One way to overcome this is fine-grained includes that are being pursued separately. Another way is to employ clang's precompiled headers support which this PR is doing. Those two approaches can be combined, and this PR adds test-e2e/PerformanceTests/KernelCompiler/auto-pch.cpp that gives some idea of the PCH impact. The test shows PCH benefits when compiling some of the fine-grained includes on top of absolute minimum required to compiled SYCL RTC's "Hello world". From one of the CI runs:

Extra Headers	Without PCH	With auto-PCH
	176ms 137ms 136ms 136ms 136ms	226ms 64ms 64ms 64ms 64ms
sycl/half_type.hpp	165ms 165ms 165ms 165ms 165ms	267ms 71ms 72ms 72ms 72ms
sycl/ext/oneapi/bfloat16.hpp	174ms 173ms 173ms 173ms 173ms	279ms 76ms 73ms 73ms 74ms
sycl/marray.hpp	142ms 143ms 142ms 142ms 143ms	235ms 66ms 66ms 66ms 66ms
sycl/vector.hpp	296ms 290ms 290ms 290ms 290ms	487ms 124ms 125ms 125ms 125ms
sycl/multi_ptr.hpp	278ms 278ms 276ms 275ms 274ms	441ms 125ms 125ms 125ms 125ms
sycl/builtins.hpp	537ms 533ms 531ms 531ms 531ms	883ms 218ms 218ms 219ms 218ms

It misses sycl/sycl.hpp line because that currently crashes FE when reading the generated PCH, the crash is being investigated/fixed separately.

Implementation-wise I'm reusing existing upstream clang::PrecompiledPreamble with one minor modification. It seems that PrecompiledPreamble's main usage is for things like clangd so it ignores errors in the code. I've modified it so that those errors would break pch-generation the same way normal compilation would break. I'm also not sure if we'd want that long-term, because it seems that making such "auto-pch" persistent would deviate from the upstream version of PrecompiledPreamble even more. I can imagine that in some near future we'd need to "fork" it into a separate utility. Still, seems to be fine for the first step.

Driver modifications are for the --auto-pch option support that should only be present on the SYCL RTC path and not for the regular clang invocations from the command line. I'm relatively confident those will stay in future.

[gmlueck]

Cool! This seems like a great feature. I have some comments / questions on the documentation and exact behavior, though. See below.

[gmlueck]

It misses sycl/sycl.hpp line because that currently crashes FE when reading the generated PCH, the crash is being investigated/fixed separately.

@tahonermann I assume your team is the one investigating this? I think this needs to be fixed before we can make a release with the --auto-pch option because the main use case (and the example in the documentation) does #include <sycl/sycl.hpp>. How should we handle this dependency? Is it safe to merge this PR with the expectation that the FE will be fixed before the next release? Or, should we hold this PR until there is a fix?