Fix part of #19435: Migrate Blog Admin page

[Vir-8]

Overview

1. This PR fixes part of Migration of Individual Pages from Webpack/AngularJS to Lazy-Loaded Angular Modules #19435.
2. This PR does the following: Migrates the Blog Admin page from Webpack/AngularJS to Lazy-Loaded Angular Modules

Essential Checklist

• The PR title starts with "Fix #bugnum: " or "Fix part of #bugnum: ...", followed by a short, clear summary of the changes.
• I have followed the instructions for making a code change.
• I have assigned the correct reviewers to this PR (or will leave a comment with the phrase "@{{reviewer_username}} PTAL" if I don't have permissions to assign reviewers directly).
• The linter/Karma presubmit checks pass on my local machine, and my PR follows the coding style guide).
• "Allow edits from maintainers" is checked. (See here for instructions on how to enable it.)

Proof that changes are correct

blog_admin_migration1.webm

PR Pointers

• Never force push! If you do, your PR will be closed.
• To reply to reviewers, follow these instructions: https://github.com/oppia/oppia/wiki/Make-a-pull-request#step-5-address-review-comments-until-all-reviewers-approve
• Some e2e tests are flaky, and can fail for reasons unrelated to your PR. We are working on fixing this, but in the meantime, if you need to restart the tests, please check the "If your build fails" wiki page.
• See the Code Owner's wiki page for what code owners will expect.

[oppiabot]

Assigning @kevintab95 for the first pass review of this PR. Thanks!

[DubeySandeep]

@Vir-8 Thanks for the PR, the changes look great! 😮

I've left a few minor comments, PTAL!

[oppiabot]

Hi @Vir-8, it looks like some changes were requested on this pull request by @DubeySandeep. PTAL. Thanks!

[Vir-8]

@DubeySandeep thanks for the review! I've made the changes, PTAL

[oppiabot]

Unassigning @Vir-8 since a re-review was requested. @Vir-8, please make sure you have addressed all review comments. Thanks!

[oppiabot]

Unassigning @DubeySandeep since they have already approved the PR.

[DubeySandeep]

@Vir-8 Would you like to pick one more from #19435 ? (optional) If yes, please leave a comment in the issue and start working on it (on a separate branch).

Thanks again for helping out on #19435 :)

[kevintab95]

LGTM for codeowner files. Thanks @Vir-8!

[oppiabot]

Hi @Vir-8, 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!