Fix part of #5025: App and OS Deprecation Milestone 2 - Add protos and the DeprecationController

[kkmurerwa]

Explanation

Fix part of #5025: When this PR is merged, it will;

• Add a new deprecation.proto file that will allow the storage of deprecation responses as well as provide the various deprecation types.
• Add the OPTIONAL_UPDATE_AVAILABLE and the OS_IS_DEPRECATED startup modes on the onboarding.proto file for the two new startup modes being introduced.
• Create a DeprecationController class and add tests for the class in the DeprecationControllerTest.
• Modify BUILD.bazel files to provide the new proto files and the deprecation controller.
• Add DeprecationControllerTest to the OppiaParameterizedTestRunner file exemptions on the file_content_validation_checks.textproto.

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

[kkmurerwa]

Hey @BenHenning and @adhiamboperes. Here is the PR for the second milestone of the App/OS Deprecation Feature. PTAL.

[BenHenning]

Thanks @kkmurerwa! I'm going to be delegating this over to @adhiamboperes to approve since she'll be stepping in for me for codeowners starting this week through all of June.

[adhiamboperes]

Thanks @kkmurerwa.
I have only reviewed the protos since there are changes that may cause you to update some parts of your implementation. I have suggested a way to structure your deprecation responses, and also requested changes to the field documentation since some of the comments are not clear to me. I think we should aim for clarity on how these models are used because this is impotant for maintenability.

[oppiabot]

Unassigning @adhiamboperes since the review is done.

[oppiabot]

Hi @kkmurerwa, it looks like some changes were requested on this pull request by @adhiamboperes. PTAL. Thanks!

[kkmurerwa]

Hey @adhiamboperes. This is ready for another pass. PTAL.

[adhiamboperes]

Hi @kkmurerwa, I have requested some changes, most of which are suggestins for improvements. PTAL, thanks.

[oppiabot]

Unassigning @adhiamboperes since the review is done.

[oppiabot]

Hi @kkmurerwa, it looks like some changes were requested on this pull request by @adhiamboperes. PTAL. Thanks!

[adhiamboperes]

Hi @kkmurerwa, I have left a few further comments+some previoujs comments are not yet resolved. PTAL!

[kkmurerwa]

Hi @adhiamboperes. I have pushed an updated commit. Let me know if something else is remaining.

[adhiamboperes]

Hi @kkmurerwa I have left one additional comment, but otherwise this LGTM.

[oppiabot]

Unassigning @adhiamboperes since they have already approved the PR.

[oppiabot]

Hi @kkmurerwa, this PR is ready to be merged. Please address any remaining comments prior to merging, and feel free to ask someone to merge your PR once the CI checks pass and you're happy with it. Thanks!