feat: allow TTL to be a duration in days, weeks, etc..

[iTrooz]

Thank you for contributing to Velero!

Please add a summary of your change

This PR changes the type used to parse TTLs, allowing parsing types largers than hours. The most obvious benefit is to allow days, but I also added weeks, months, and years

Does your change fix a particular issue?

No

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file (make new-changelog) or comment /kind changelog-not-required on this PR.
• Updated the corresponding documentation in site/content/docs/main.

Notes

For now, this feature has the following limitations:

• Only applies to the TTL parameter, and not other Duration-based parameters
• Only apply to the CLI flag, and not the CRD fields

I would be glad to add these changes, if there is an interest for it

[reasonerjt]

Is this really needed?

[iTrooz]

Is this really needed?

I believe so, entering backup TTL in hours can be annoying/error prone. For example, I wanted to create a 30d backup TTL for my personal cluster, and "30d" is more readable than "720h"

But this is clearly a quality-of-life addition, it doesn't allow new things

[kaovilai]

don't forget to regenerate crd :)

[iTrooz]

Whoops, thank you

[codecov]

Codecov Report

❌ Patch coverage is 75.55556% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.91%. Comparing base (e6aab8c) to head (b3e0744).
⚠️ Report is 64 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/cmd/util/flag/duration.go	76.19%	9 Missing and 1 partial ⚠️
pkg/cmd/cli/schedule/create.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9345      +/-   ##
==========================================
+ Coverage   59.67%   59.91%   +0.23%     
==========================================
  Files         383      384       +1     
  Lines       44079    34991    -9088     
==========================================
- Hits        26306    20966    -5340     
+ Misses      16223    12479    -3744     
+ Partials     1550     1546       -4     

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[kaovilai]

some further doc or implementation changes I think are needed.

[iTrooz]

Hello ! Could someone else please review this PR ?
@sseago @ywk253100