Add "create_branch" and "delete_branch" endpoints

[Wauplin]

Resolve #1165. Follow moon-landing implementation https://github.com/huggingface/moon-landing/pull/4395 (internal link)

This PR adds create_branch and delete_branch methods to HfApi client.

---

@severo: It is not documented since only available for HF users but I was able to create the /refs/convert/parquet branch with it:

from huggingface_hub import create_branch, create_repo

repo_id = "Wauplin/tmp_to_delete_branch_creation"

create_repo(repo_id)
create_branch(repo_id, branch="refs/convert/parquet")

=> https://huggingface.co/Wauplin/tmp_to_delete_branch_creation/tree/refs%2Fconvert%2Fparquet

[HuggingFaceDocBuilder]

The documentation is not available anymore as the PR was closed or merged.

[codecov]

Codecov Report

Base: 83.93% // Head: 84.01% // Increases project coverage by +0.07% 🎉

Coverage data is based on head (e0149ef) compared to base (7e10549).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1181      +/-   ##
==========================================
+ Coverage   83.93%   84.01%   +0.07%     
==========================================
  Files          43       43              
  Lines        4282     4303      +21     
==========================================
+ Hits         3594     3615      +21     
  Misses        688      688              

Impacted Files	Coverage Δ
src/huggingface_hub/hf_api.py	88.41% <100.00%> (+0.31%)	⬆️

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[julien-c]

nice one! 🎉