Kotlin tests: roll Kotlin1 suites forward to language-version 2.0

Why this is needed:
- The extractor compatibility fixes now preserve the information these Kotlin1-era
  tests were protecting, even when compiled with Kotlin 2.4 and
  `-language-version 2.0`.
- Keeping mixed legacy language-version wiring in individual tests is no longer
  necessary and obscures the intended steady-state execution mode.

What this changes:
- Update all affected Kotlin1 compatibility integration tests to run with
  `-language-version 2.0` directly.
- Keep the expected extraction signal aligned for extractor information output.
- Remove the obsolete CODEOWNERS entry for the retired `java/ql/test-kotlin1/`
  path.

This consolidates the language-version transition into a single test rollup
commit, as requested.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

java/ql/integration-tests/kotlin/all-platforms/enhanced-nullability/test.py

@@ -1,11 +1,11 @@
 import pathlib
 
 
-def test(codeql, java_full, kotlinc_2_3_20):
+def test(codeql, java_full):
     java_srcs = " ".join([str(s) for s in pathlib.Path().glob("*.java")])
     codeql.database.create(
         command=[
             f"javac {java_srcs} -d build",
-            "kotlinc -language-version 1.9 user.kt -cp build",
+            "kotlinc -language-version 2.0 user.kt -cp build",
         ]
     )

java/ql/integration-tests/kotlin/all-platforms/external-property-overloads/test.py

@@ -1,6 +1,6 @@
 import commands
 
 
-def test(codeql, java_full, kotlinc_2_3_20):
-    commands.run("kotlinc -language-version 1.9 test.kt -d lib")
-    codeql.database.create(command="kotlinc -language-version 1.9 user.kt -cp lib")
+def test(codeql, java_full):
+    commands.run("kotlinc -language-version 2.0 test.kt -d lib")
+    codeql.database.create(command="kotlinc -language-version 2.0 user.kt -cp lib")

java/ql/integration-tests/kotlin/all-platforms/extractor_information_kotlin1/ExtractorInformation.expected

@@ -9,4 +9,4 @@
 | Percentage of calls with call target | 100 |
 | Total number of lines | 3 |
 | Total number of lines with extension kt | 3 |
-| Uses Kotlin 2: false | 1 |
+| Uses Kotlin 2: true | 1 |

java/ql/integration-tests/kotlin/all-platforms/extractor_information_kotlin1/test.py

@@ -1,2 +1,2 @@
-def test(codeql, java_full, kotlinc_2_3_20):
-    codeql.database.create(command=f"kotlinc -J-Xmx2G -language-version 1.9 SomeClass.kt")
+def test(codeql, java_full):
+    codeql.database.create(command="kotlinc -J-Xmx2G -language-version 2.0 SomeClass.kt")

java/ql/integration-tests/kotlin/all-platforms/file_classes/test.py

@@ -1,6 +1,6 @@
 import commands
 
 
-def test(codeql, java_full, kotlinc_2_3_20):
-    commands.run("kotlinc -language-version 1.9 A.kt")
-    codeql.database.create(command="kotlinc -cp . -language-version 1.9 B.kt C.kt")
+def test(codeql, java_full):
+    commands.run("kotlinc -language-version 2.0 A.kt")
+    codeql.database.create(command="kotlinc -cp . -language-version 2.0 B.kt C.kt")

java/ql/integration-tests/kotlin/all-platforms/java-interface-redeclares-tostring/test.py

@@ -1,6 +1,6 @@
 import commands
 
 
-def test(codeql, java_full, kotlinc_2_3_20):
+def test(codeql, java_full):
     commands.run(["javac", "Test.java", "-d", "bin"])
-    codeql.database.create(command="kotlinc -language-version 1.9 user.kt -cp bin")
+    codeql.database.create(command="kotlinc -language-version 2.0 user.kt -cp bin")

java/ql/integration-tests/kotlin/all-platforms/kotlin_java_lowering_wildcards/test.py

@@ -1,13 +1,13 @@
 import commands
 
 
-def test(codeql, java_full, kotlinc_2_3_20):
+def test(codeql, java_full):
     # Compile the JavaDefns2 copy outside tracing, to make sure the Kotlin view of it matches the Java view seen by the traced javac compilation of JavaDefns.java below.
     commands.run(["javac", "JavaDefns2.java"])
     codeql.database.create(
         command=[
             "kotlinc kotlindefns.kt",
             "javac JavaUser.java JavaDefns.java -cp .",
-            "kotlinc -language-version 1.9 -cp . kotlinuser.kt",
+            "kotlinc -language-version 2.0 -cp . kotlinuser.kt",
         ]
     )