[mlgo-utils] Create symlinked entrypoints in root directory (#146981)

These scripts belong in the `mlgo-utils` directory when directly used
with python3. But since they are also used to package with pip, symlink
the entrypoint scripts to mlgo-utils directory. Adjust the bazel paths
to account for this as well. This loosely follows the same structure as lit.

Verified that I was also able to build the package successfully and use
the script.

Author: thevinster

llvm/utils/mlgo-utils/combine_training_corpus.py

@@ -0,0 +1 @@
+mlgo/corpus/combine_training_corpus.py

llvm/utils/mlgo-utils/extract_ir.py

@@ -0,0 +1 @@
+mlgo/corpus/extract_ir.py

llvm/utils/mlgo-utils/make_corpus.py

@@ -0,0 +1 @@
+mlgo/corpus/make_corpus.py

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

@@ -5236,8 +5236,8 @@ py_binary(
 py_binary(
     name = "extract_ir",
     srcs = [
+        "utils/mlgo-utils/extract_ir.py",
         "utils/mlgo-utils/mlgo/__init__.py",
-        "utils/mlgo-utils/mlgo/corpus/extract_ir.py",
         "utils/mlgo-utils/mlgo/corpus/extract_ir_lib.py",
         "utils/mlgo-utils/mlgo/corpus/flags.py",
     ],
@@ -5247,8 +5247,8 @@ py_binary(
 py_binary(
     name = "combine_training_corpus",
     srcs = [
+        "utils/mlgo-utils/combine_training_corpus.py",
         "utils/mlgo-utils/mlgo/__init__.py",
-        "utils/mlgo-utils/mlgo/corpus/combine_training_corpus.py",
         "utils/mlgo-utils/mlgo/corpus/combine_training_corpus_lib.py",
         "utils/mlgo-utils/mlgo/corpus/flags.py",
     ],
@@ -5258,8 +5258,8 @@ py_binary(
 py_binary(
     name = "make_corpus",
     srcs = [
+        "utils/mlgo-utils/make_corpus.py",
         "utils/mlgo-utils/mlgo/__init__.py",
-        "utils/mlgo-utils/mlgo/corpus/make_corpus.py",
         "utils/mlgo-utils/mlgo/corpus/make_corpus_lib.py",
     ],
     imports = ["utils/mlgo-utils"],