More frozen resources and dead code removals

Background
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This pull request achieves the following two things:

* Addressed review comments in [a previous pull request](https://github.com/DynamoDS/Dynamo/pull/1635)
* Moved various ```SolidColorBrush``` objects into ```FrozenResources``` to avoid memory leaks
* Removed all unnecessary codes that were used in the legacy info bubble
* Removed unwanted test cases for the legacy info bubble

Further Works
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With regards to the memory leak part, more extensive works can be found on a temporary branch -- [```Plumber```](https://github.com/Benglin/Dynamo/compare/Plumber). The ```Plumber``` branch is not ready for merging yet but it resembles what will ultimately resolve most issues surrounding static references to objects. These objects that are being referenced directly or indirectly by static objects survive garbage collections, making them stay across multiple unit test runs. This results in unit tests going out of memory.