[XRay][compiler-rt] Remove more STL dependenices from FDR mode

Summary:
This change removes dependencies on STL types:

  - std::aligned_storage -- we're using manually-aligned character
    buffers instead for metadata and function records.

  - std::tuple -- use a plain old struct instead.

This is an incremental step in removing all STL references from the
compiler-rt implementation of XRay (llvm.org/PR32274).

Reviewers: dblaikie, pelikan, kpw

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39277

llvm-svn: 316816