MacOS: Use unique identifier for each JBR family

All MacOS .pkg files for the JBR currently include `identifier="com.jetbrains.jbr"` which may cause issues when multiple versions are installed / will break uninstalls.

Please consider transitioning to something like `identifier="com.jetbrains.jbr$majorversion"` so that multiple installs can be supported more cleanly (e.g. in homebrew casks).

Ex:
```
com.jetbrains.jbr25
com.jetbrains.jbr21
com.jetbrains.jbr17
```

Start by locating the macOS .pkg packaging configuration and the entry point that sets the current com.jetbrains.jbr identifier. Check how major JBR versions are available to the packaging process, then verify that each family receives a distinct identifier and that multiple versions can be installed and uninstalled independently.

Written by the indexing model from the issue text.