dlltrace: Implement dll path override.
dlltrace: Implement dll path override.

Implement env var APITRACE_FORCE_MODULE_PATH which allows the user to
force override the directory to the dirs we want to trace against.This
is useful for tracing against reimplementations (ie. d9vk/dxvk) on their
native platforms.

apitrace/apitrace,apitrace/apitrace,apitrace/apitrace,apitrace/apitrace