Generate instrumentation packages setup.py files (#474)

All instrumentations packages have almost exactly same setup.py files.
This commit adds a python script that generates it from a source
template. This dramatically reduces the time and effort required to
update all instrumentation setup.py files, and also reduces chances of
making manual mistakes.

scripts/generate_setup.py

@@ -0,0 +1,77 @@
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import os
+import subprocess
+
+from jinja2 import Template
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger("setupy_generator")
+
+_auto_generation_msg = """
+# DO NOT EDIT. THIS FILE WAS AUTOGENERATED FROM templates/{source}.
+# RUN `python scripts/generate_setup.py` TO REGENERATE.
+"""
+_template_dir = "templates"
+_template_name = "instrumentation_setup.py.txt"
+_prefix = "opentelemetry-instrumentation-"
+
+
+def main():
+    root_path = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+    setuppy_tmpl = Template(
+        open(
+            os.path.join(root_path, _template_dir, _template_name), "r"
+        ).read()
+    )
+    base_instrumentation_path = os.path.join(root_path, "instrumentation")
+
+    for instrumentation in os.listdir(base_instrumentation_path):
+        instrumentation_path = os.path.join(
+            base_instrumentation_path, instrumentation
+        )
+        if not os.path.isdir(
+            instrumentation_path
+        ) or not instrumentation.startswith(_prefix):
+            continue
+
+        src_dir = os.path.join(
+            instrumentation_path, "src", "opentelemetry", "instrumentation"
+        )
+        src_pkgs = [
+            f
+            for f in os.listdir(src_dir)
+            if os.path.isdir(os.path.join(src_dir, f))
+        ]
+        assert len(src_pkgs) == 1
+        name = src_pkgs[0]
+        generated = setuppy_tmpl.render(
+            name=name,
+            auto_generation_msg=_auto_generation_msg.format(
+                source=_template_name
+            ),
+        )
+
+        generated_file = os.path.join(instrumentation_path, "setup.py")
+        logger.info("generated %s", generated_file)
+        with open(generated_file, "w") as fh:
+            fh.write(generated)
+            fh.flush()
+        subprocess.run(["black", "-q", generated_file], check=True)
+
+
+if __name__ == "__main__":
+    main()