Migrate core Hera classes to dataclasses (dropping Pydantic)

[elliotgunton]

Pull Request Checklist

• Fixes Migrate Hera classes and related internals off Pydantic V1 #1544
• Tests added
• Documentation/examples added
• Good commit messages and/or PR title

Description of PR
This PR will be used as the base branch for #1544, starting in this PR with the Archive, Env and EnvFrom classes being converted to dataclasses as they are the simplest classes that show the proof of concept for converting to dataclasses (in this case, it's effectively a "one-liner" to remove the BaseModel parent class and use @dataclass instead). And then continuing with the internals of Hera which can be converted without generating new API classes. We can then generate those API classes and fix the minor issues that appear.

[codecov]

Codecov Report

❌ Patch coverage is 92.61745% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.1%. Comparing base (5dc9eaa) to head (0b38d1b).
⚠️ Report is 24 commits behind head on main.

Files with missing lines	Patch %	Lines
src/hera/workflows/volume.py	92.7%	9 Missing and 6 partials ⚠️
src/hera/workflows/resources.py	82.3%	1 Missing and 5 partials ⚠️
src/hera/workflows/env.py	93.3%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1547     +/-   ##
=======================================
+ Coverage   80.4%   81.1%   +0.6%     
=======================================
  Files         63      63             
  Lines       5144    5267    +123     
  Branches     821     824      +3     
=======================================
+ Hits        4140    4273    +133     
+ Misses       858     847     -11     
- Partials     146     147      +1     

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[jeongukjae]

Looks good! 👍