Swift: add SuccessfullyExtractedLines query

This counts how many lines we have extracted some entity in. If we test
changes in this, we can have a more fine grained look into how much we
actually extract than looking at the extracted files.

swift/ql/src/diagnostics/SuccessfullyExtractedLines.ql

@@ -0,0 +1,15 @@
+/**
+ * @name Successfully extracted lines
+ * @description Count all lines in source code in which something was extracted.
+ * @kind metric
+ * @id swift/diagnostics/successfully-extracted-lines
+ * @tags summary
+ */
+
+import swift
+
+select count(File f, int line |
+    exists(Location loc |
+      not loc instanceof UnknownLocation and loc.getFile() = f and loc.getStartLine() = line
+    )
+  )

swift/ql/test/query-tests/Diagnostics/SuccessfullyExtractedLines.expected

@@ -0,0 +1 @@
+| 4 |

swift/ql/test/query-tests/Diagnostics/SuccessfullyExtractedLines.qlref

@@ -0,0 +1 @@
+diagnostics/SuccessfullyExtractedLines.ql

swift/ql/test/query-tests/Diagnostics/ignored.swift

@@ -0,0 +1,3 @@
+//codeql-extractor-env: CODEQL_EXTRACTOR_SWIFT_RUN_UNDER=true
+
+func not_compiled() {}

swift/ql/test/query-tests/Diagnostics/main.swift

@@ -0,0 +1,6 @@
+
+
+// a comment
+
+
+func foo() {}