PY-15701 Allow to specify minimum number of blank lines after local imports

Add new option "After local imports" on "Blank lines" tab of Python
code style settings.

python/testData/addImport/localFromImport.after.py

@@ -1,6 +1,5 @@
 def func():
     for _ range(10):
         from package.module import foo
-
         foo
 #       <ref>

python/testData/addImport/localImport.after.py

@@ -1,7 +1,6 @@
 def func():
     try:
         import module
-
         module
 #       <ref>
     except:

python/testData/addImport/localImportInlineBranch.after.py

@@ -1,6 +1,5 @@
 def func():
     if True:
         import module
-
         module
 #            <ref>

python/testData/addImport/localImportInlineFunctionBody.after.py

@@ -1,5 +1,4 @@
 def func():
     import module
-
     module
 #           <ref>

python/testData/formatter/noBlankLinesAfterLocalImports.py

@@ -0,0 +1,13 @@
+from pprint import pprint
+VAR = 42
+def foo():
+    import sys
+    import ast, tokenize
+    pass
+
+
+class C:
+    from textwrap import dedent
+    pass
+    import codecs as C
+    pass

python/testData/formatter/noBlankLinesAfterLocalImports_after.py

@@ -0,0 +1,16 @@
+from pprint import pprint
+
+VAR = 42
+
+
+def foo():
+    import sys
+    import ast, tokenize
+    pass
+
+
+class C:
+    from textwrap import dedent
+    pass
+    import codecs as C
+    pass