Refactor product handling logic in build script

[Lootwig]

Adds handling for the "IU" (Idea Ultimate) product variant, currently skipped over and failing builds due to android plugin dependency logic being tied to "IC". This conflicts with the contributing.md:

...

1. Make sure you're using the latest stable release of IntelliJ,
   or download and install the latest version of IntelliJ (2023.1 or later).

   • IntelliJ Downloads
   • Either the community edition (free) or Ultimate will work. <-- no it won't

2. Create a gradle.properties file.
   ...

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read the [Flutter Style Guide] recently, and have followed its advice.
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• All existing and new tests are passing.