[uwptool] Move Launch, Uninstall to AppStore class

[cbracken]

This refactoring moves the Application Launch and Uninstall methods to
the ApplicationStore class. This simplifies writing tests for Command
classes since the Application class is now a plain old data class, and
ApplicationStore can be replaced with a fake implementation for hermetic
testing, while I'll do in a follow-up patch.

This is a refactoring that introduces no changes to existing functionality.
Functionality is covered by existing tests.

Issue: flutter/flutter#83072

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 and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See testing the engine for instructions on
  writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.
• The reviewer has submitted any presubmit flakes in this PR using the engine presubmit flakes form before re-triggering the failure.

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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[cbracken]

@clarkezone This patch is stacked on top of #26309. You only need to review the second of the two patches in this PR. Once the above patch lands, I'll rebase this against tip-of-tree.

[clarkezone]

LGTE