[LLD] Remove global state in lld/COFF

[LLD] Remove global state in lld/COFF

Remove globals from the lldCOFF library, by moving globals into a context class.
This patch mostly moves the config object into COFFLinkerContext.

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

Reviewed By: aganea

Differential Revision: https://reviews.llvm.org/D110450