Xray Migration Tool should not map IDs from unrelated projects

In some scenarios, the IDs are mapped even from projects that are not related to the current project being imported. Note: The ID mapping is necessary to recreate associations that existed in the Jira-Origin.

Let's take this scenario as example: (Jira-Origin is where the backup file is generated, Jira-Target is where the project is imported)

• Jira-Origin with the following projects: A, B, C, D
• In the last days there were some migration processes to import the projects A, B, C from Jira-Origin to Jira-Target
• Now Jira-Target has the following projects: A, B, C
• If the admin now starts the migration for the project D, because project A, B and C are in the backup file and in the Jira-Target, Xray will process the ID mappings for these projects, even if they do not have any association with project D.

This is unnecessary processing and consumes unnecessary resources (each mapper is in-memory). 

Note: Even if project D is not an Xray project nor is used for Requirement Coverage, nor has associations to other Xray projects, the Xray import handlers will still be called and the mappings will be processed.