[ZEPPELIN-6462] Close interpreter-setting.json streams with try-with-resources

[big-cir]

What is this PR for?

InterpreterSettingManager discovers interpreters by reading each interpreter's interpreter-setting.json. Two helpers do this, and neither closes the stream it opens:

// registerInterpreterFromResource
getInterpreterListFromJson(url.openStream());

// registerInterpreterFromPath
getInterpreterListFromJson(new FileInputStream(interpreterJsonPath.toFile()));

The shared sink wraps the stream in an InputStreamReader and hands it to gson.fromJson(...). Gson does not close a reader passed to it — the caller owns it — so the descriptor leaks on the normal path. There is no finally or try-with-resources either, so it also leaks when parsing throws, for example a JsonSyntaxException from a malformed setting file.

This is not limited to startup. After installing an interpreter through POST /api/interpreter/install, InterpreterService.downloadInterpreter() calls refreshInterpreterTemplates(), which re-runs the whole directory scan. Every install therefore leaks one descriptor per interpreter directory, and the leaks accumulate on a long-running server.

This PR wraps each stream in a try-with-resources at the call site that opens it. Parsing and registration behaviour is unchanged.

What type of PR is it?

Bug Fix

Todos

• Close the stream opened in registerInterpreterFromResource
• Close the stream opened in registerInterpreterFromPath
• Cover both the normal path and the parse-failure path with tests

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-6462

How should this be tested?

Three tests were added to InterpreterSettingManagerTest:

• testRegisterInterpreterFromPathClosesStream
• testRegisterInterpreterFromResourceClosesStream
• testStreamIsClosedWhenParsingFails

./mvnw package -pl zeppelin-server --am -Dtest=InterpreterSettingManagerTest -DfailIfNoTests=false

With the try-with-resources reverted, all three fail:

[ERROR] Tests run: 14, Failures: 3
  testRegisterInterpreterFromPathClosesStream      Wanted but not invoked: ...close()
  testRegisterInterpreterFromResourceClosesStream  Wanted but not invoked: ...close()
  testStreamIsClosedWhenParsingFails               Wanted but not invoked: ...close()

With the fix in place: Tests run: 14, Failures: 0.

InterpreterFactoryTest, InterpreterSettingTest and InterpreterServiceTest also pass (18 tests).

Screenshots (if appropriate)

N/A

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No