feat(backend): remove reactions fully on account deletion

[Mar0xy]

What

This PR will make sure to remove reactions fully when someone deletes their account.

Why

Fixes #11906

Additional info (optional)

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

Attention: 31 lines in your changes are missing coverage. Please review.

Comparison is base (780b120) 78.72% compared to head (baf162c) 78.68%.

Files	Patch %	Lines
.../queue/processors/DeleteAccountProcessorService.ts	18.42%	31 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #12249      +/-   ##
===========================================
- Coverage    78.72%   78.68%   -0.04%     
===========================================
  Files          951      950       -1     
  Lines       103311   103284      -27     
  Branches      8301     8303       +2     
===========================================
- Hits         81332    81274      -58     
- Misses       21979    22010      +31     

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[github-actions]

このPRによるapi.jsonの差分

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[Mar0xy]

Bug is still valid as of latest version.

[Mar0xy]

@kakkokari-gtyih Is the code okay like this or should something be changed?

Also I noticed in the recent blog post about misskey's 2023 year there was a mention of trying to become GDPR compliant next year and we(Sharkey) have a GDPR related feature for letting users get all their stored data and I wonder if there is any interest in having it merged.
https://github.com/transfem-org/Sharkey/blob/develop/packages/backend/src/queue/processors/ExportAccountDataProcessorService.ts

[kakkokari-gtyih]

I am not an expert on the backend so I cannot determine this, so let me ask @syuilo about these instead.

[kakkokari-gtyih]

@syuilo 👀👀👀