Revert "[llvm-cov] Add support for baseline coverage" (#144121)

Reverts llvm/llvm-project#117910

```
/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/unittests/ProfileData/CoverageMappingTest.cpp
/home/buildbots/llvm-external-buildbots/workers/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/llvm/unittests/ProfileData/CoverageMappingTest.cpp:281:28: error: 'std::reference_wrapper' may not intend to support class template argument deduction [-Werror,-Wctad-maybe-unsupported]
  281 |         std::make_optional(std::reference_wrapper(*ProfileReader));
      |                            ^
/usr/lib/gcc/ppc64le-redhat-linux/8/../../../../include/c++/8/bits/refwrap.h:289:11: note: add a deduction guide to suppress this warning
  289 |     class reference_wrapper
      |           ^
```

1 files changed, 1 insertions, 3 deletions

diff --git a/llvm/unittests/ProfileData/CoverageMappingTest.cpp b/llvm/unittests/ProfileData/CoverageMappingTest.cpp
index c0e99cf..46f881e 100644
--- a/llvm/unittests/ProfileData/CoverageMappingTest.cpp
+++ b/llvm/unittests/ProfileData/CoverageMappingTest.cpp
@@ -277,9 +277,7 @@ struct CoverageMappingTest : ::testing::TestWithParam<std::tuple<bool, bool>> {
       CoverageReaders.push_back(
           std::make_unique<CoverageMappingReaderMock>(Funcs));
     }
-    auto ProfileReaderRef =
-        std::make_optional(std::reference_wrapper(*ProfileReader));
-    return CoverageMapping::load(CoverageReaders, ProfileReaderRef);
+    return CoverageMapping::load(CoverageReaders, *ProfileReader);
   }
 
   Error loadCoverageMapping(bool EmitFilenames = true) {