[Do not merge yet] Update documentation for feature flags and feature launch process.

[seanlip]

Explanation

This PR updates the wiki based on discussions with @BenHenning about the feature launch process. In writing this up, I realized that several things need to be done/clarified:

• [ ] Web needs to specify a required min-Android-app-version for prod-stage Android feature flags (i.e. beta and GA).
• [ ] Do flags have a dev/test/prod stage on Android as well as Web? If so, how will the two be kept in sync -- does the developer need to do this manually? What if they are not in sync? This needs to be documented here.
• [ ] We need to set up the Android feature testing team so that the form mentioned in step 3 of the pre-launch testing stage instructions actually goes somewhere.

Nevertheless I would like to get a preliminary review of this PR so it's clear what else needs to be addressed before this can be merged (and which of the above is fine to address post-merge).

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: ...".)
• [x] Any changes to scripts/assets files have their rationale included in the PR explanation.
• [x] The PR follows the style guide.
• [x] The PR does not contain any unnecessary code changes from Android Studio (reference).
• [x] The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• [x] The PR is assigned to the appropriate reviewers (reference).

[oppiabot[bot]]

Hi @seanlip, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue. If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[oppiabot[bot]]

Hi @seanlip, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue. If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[oppiabot[bot]]

Hi @seanlip, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue. If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!

[oppiabot[bot]]

Hi @seanlip, I'm going to mark this PR as stale because it hasn't had any updates for 7 days. If no further activity occurs within 7 days, it will be automatically closed so that others can take up the issue. If you are still working on this PR, please make a follow-up commit within 3 days (and submit it for review, if applicable). Please also let us know if you are stuck so we can help you!