chore: hide developer tokens section in if there is nothing to display or create

[rob006]

Possible implementation for https://discuss.flarum.org/d/32531-hide-developer-tokens-section-in-security-view-if-user-cant-create-tokens.

It hides this section if user does not have permission to create or moderate tokens, and list of tokens is empty. LoadingIndicator is displayed until list of tokens is loaded.

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

Required changes:

• Related documentation PR: (Remove if irrelevant)
• Related core extension PRs: (Remove if irrelevant)

[SychO9]

Thanks for the PR!