fix(files): support submenu in batch actions header too

[skjnldsv]

Supersede #45525

Summary

• Add support for subactions on the header
• Fixed handling of actions and unified some processes between file actions and selection actions
• Added cypress tests:
  • Standard file actions
  • Nested file actions
  • Selection file actions
  • Nested selection actions

[skjnldsv]

/backport to stable31

[skjnldsv]

/compile rebase-amend /

[skjnldsv]

/backport to stable31

[backportbot]

The backport to stable31 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable31
git pull origin stable31

# Create the new backport branch
git checkout -b backport/50364/stable31

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick e10947a5 73e4a13a d8df001f

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/50364/stable31

Error: Failed to create pull request: Validation Failed: {"resource":"PullRequest","code":"custom","message":"A pull request already exists for nextcloud:backport/50364/stable31."}

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.