[clang][tooling] Accept Clang invocations with multiple jobs

When `-fno-integrated-as` is passed to the Clang driver (or set by default by a specific toolchain), it will construct an assembler job in addition to the cc1 job. Similarly, the `-fembed-bitcode` driver  flag will create additional cc1 job that reads LLVM IR file.

The Clang tooling library only cares about the job that reads a source file. Instead of relying on the fact that the client injected `-fsyntax-only` to the driver invocation to get a single `-cc1` invocation that reads the source file, this patch filters out such jobs from `Compilation` automatically and ignores the rest.

This fixes a test failure in `ClangScanDeps/headerwithname.cpp` and `ClangScanDeps/headerwithnamefollowedbyinclude.cpp` on AIX reported here: https://reviews.llvm.org/D103461#2841918 and `clang-scan-deps` failures with `-fembed-bitcode`.

Depends on D106788.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D105695