add S3 minimum part size defined by the user

[rvrangel]

Description

This adds a new parameter to allow the operator to specify a minimum part size for the S3 uploads.

Related Issue(s)

fixes #17175

Checklist

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• Documentation was added or is not required

Deployment Notes

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[codecov]

Codecov Report

Attention: Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.

Project coverage is 67.39%. Comparing base (0b51839) to head (5994e0e).

Files with missing lines	Patch %	Lines
go/vt/mysqlctl/s3backupstorage/s3.go	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17171      +/-   ##
==========================================
+ Coverage   67.37%   67.39%   +0.01%     
==========================================
  Files        1573     1573              
  Lines      253113   253130      +17     
==========================================
+ Hits       170538   170592      +54     
+ Misses      82575    82538      -37     

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[mattlord]

LGTM. Just a couple of minor comments.

[mattlord]

Nit, but we use min in other existing flags so we can shorten this one as well. New flags should also use dashes rather than underscores as we want to transition to the latter for everything.

[mattlord]

Since this flag is part of a group... we may actually just want to keep them all uniform...

[rvrangel]

I can change it to min, but do let me know if the preferred is to use the dashes instead of underscores for it :)

[mattlord]

I would favor uniformity for this config group over moving to dashes, and move these all together.

[frouioui]

I would probably spell out what the default is and add a period to be consistent with other flags in the same group. The default shown by the helper is not very intuitive at first.

[rvrangel]

updated it :)

[mattlord]

Where do these min and max values come from? I would hope that there are consts we can use instead?

[rvrangel]

that's a great point. for the minimum, the SDK does define it, so we could use manager.MinUploadPartSize, but I don't see anything for the max. I will take a better look when I update the code for the flag change mentioned above, but we can at least change that one

[frouioui]

It would be better to use the constant provided by the SDK for the minimum. For the maximum there is none, it's fine to hardcode it but it should be a constant for clarity with a link to AWS's docs: https://docs.aws.amazon.com/AmazonS3/latest/userguide/qfacts.html

[rvrangel]

update it as well :)