Improve test coverage of startIde

Description

Follow up based on gitlab!154584 (comment 1937417619), improve the test coverage of startIde by adding a test case for when useNewWebIde feature flag is false.

Acceptance Criteria

• Add unit test for the the case when useNewWebIde flag is false

Technical Requirements

• Involves extracting initLegacyWebIde logic to separate files for mocking purposes