Reland "[LLD] Remove global state in lld/COFF" after fixing asan and msan test failures

Original commit description:

  [LLD] Remove global state in lld/COFF

  This patch removes globals from the lldCOFF library, by moving globals
  into a context class (COFFLinkingContext) and passing it around wherever
  it's needed.

  See https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html for
  context about removing globals from LLD.

  I also haven't moved the `driver` or `config` variables yet.

  Differential Revision: https://reviews.llvm.org/D109634

This reverts commit a2fd05ad.

Original commits were b4fa71ee
and e03c7e36.