[clang-tidy] Add diagnostics level to YAML output

Summary:
Also added BuildDirectory for completness and removed unused `Fix`.

Test Plan: check-all

Reviewers: alexfh, gribozavr2

Subscribers: xazax.hun, cfe-commits

Tags: #clang-tools-extra, #clang

Differential Revision: https://reviews.llvm.org/D79285
diff --git a/clang/unittests/Tooling/DiagnosticsYamlTest.cpp b/clang/unittests/Tooling/DiagnosticsYamlTest.cpp
index ef8f3ec..acfefa5 100644
--- a/clang/unittests/Tooling/DiagnosticsYamlTest.cpp
+++ b/clang/unittests/Tooling/DiagnosticsYamlTest.cpp
@@ -65,6 +65,8 @@
     "          Offset:          100\n"
     "          Length:          12\n"
     "          ReplacementText: 'replacement #1'\n"
+    "    Level:           Warning\n"
+    "    BuildDirectory:  'path/to/build/directory'\n"
     "  - DiagnosticName:  'diagnostic#2'\n"
     "    DiagnosticMessage:\n"
     "      Message:         'message #2'\n"
@@ -75,6 +77,8 @@
     "          Offset:          62\n"
     "          Length:          2\n"
     "          ReplacementText: 'replacement #2'\n"
+    "    Level:           Warning\n"
+    "    BuildDirectory:  'path/to/build/directory'\n"
     "    Ranges:\n"
     "      - FilePath:        'path/to/source.cpp'\n"
     "        FileOffset:      10\n"
@@ -94,6 +98,8 @@
     "        FilePath:        'path/to/note2.cpp'\n"
     "        FileOffset:      99\n"
     "        Replacements:    []\n"
+    "    Level:           Warning\n"
+    "    BuildDirectory:  'path/to/build/directory'\n"
     "...\n";
 
 TEST(DiagnosticsYamlTest, serializesDiagnostics) {