Specify explicitly all exportable names from tiledbsc and remove the flake8 per-file-ignore

Reason: per-file-ignores paths are treated relative to the current directory, not the config file.
This breaks the flake8 pre-commit hook that is invoked from the project root.
See PyCQA/flake8#693

Author: gsakkis

apis/python/setup.cfg

@@ -53,5 +53,3 @@ known_third_party = anndata
 statistics = true
 ignore = E203,E501,W503,B950
 select = B,C,E,F,W,T4,B9
-per-file-ignores =
-    src/tiledbsc/__init__.py: F401

apis/python/src/tiledbsc/__init__.py

@@ -48,3 +48,23 @@
 from .uns_group import UnsGroup
 from .util_ann import describe_ann_file
 from .util_tiledb import show_soma_schemas
+
+__all__ = [
+    "AnnotationMatrix",
+    "AnnotationMatrixGroup",
+    "AnnotationPairwiseMatrixGroup",
+    "AssayMatrix",
+    "AssayMatrixGroup",
+    "RawGroup",
+    "SOMA",
+    "SOMACollection",
+    "SOMAOptions",
+    "SOMASlice",
+    "TileDBArray",
+    "TileDBGroup",
+    "TileDBObject",
+    "UnsArray",
+    "UnsGroup",
+    "describe_ann_file",
+    "show_soma_schemas",
+]