[mlir] Add missing unit tests to BUILD.bazel

Several unit test folders were missing from the bazel build, including: Transforms, Conversion, Rewrite

utils/bazel/llvm-project-overlay/mlir/unittests/BUILD.bazel

@@ -75,6 +75,20 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "rewrite_tests",
+    size = "small",
+    srcs = glob([
+        "Rewrite/*.cpp",
+        "Rewrite/*.h",
+    ]),
+    deps = [
+        "//llvm:gtest_main",
+        "//mlir:IR",
+        "//mlir:Rewrite",
+    ],
+)
+
 cc_test(
     name = "dialect_tests",
     size = "small",
@@ -243,6 +257,19 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "transforms_test",
+    size = "small",
+    srcs = glob([
+        "Transforms/*.cpp",
+        "Transforms/*.h",
+    ]),
+    deps = [
+        "//llvm:gtest_main",
+        "//mlir:TransformUtils",
+    ],
+)
+
 cc_test(
     name = "analysis_tests",
     size = "small",
@@ -260,6 +287,22 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "conversion_tests",
+    size = "small",
+    srcs = glob([
+        "Conversion/*.cpp",
+        "Conversion/*.h",
+        "Conversion/*/*.cpp",
+        "Conversion/*/*.h",
+    ]),
+    deps = [
+        "//llvm:gtest_main",
+        "//mlir:ArithmeticDialect",
+        "//mlir:PDLToPDLInterp",
+    ],
+)
+
 cc_test(
     name = "execution_engine_tests",
     size = "small",