fix(build-toolchain): migrate versioning to setuptools_scm

versioning of package now handled through setuptools_scm. Git tag therefore
takes precedence and manually setting a version in setup.cfg is redundant.

In addition, setuptools_scm handles proper inclusion of sdist non-python files
and simplifies bdist packaging.

pyproject.toml

@@ -1,7 +1,8 @@
 [build-system]
 requires = [
     "setuptools",
-    "wheel"
+    "wheel",
+    "setuptools-scm[toml]"
 ]
 build-backend = "setuptools.build_meta"
 
@@ -9,4 +10,6 @@ build-backend = "setuptools.build_meta"
 max_line_length = 80
 aggressive = 3
 recursive = true
-in-place = true
+in-place = true
+
+[tool.setuptools_scm]