[Fix] `nvm alias`: fix colors not showing by default

Colors were lost because `nvm_has_colors` checks `[ -t 1 ]`, which is false inside the `(...) | sort` pipeline in `nvm_list_aliases`.
Evaluate `nvm_has_colors` before the pipe and propagate via `NVM_HAS_COLORS`, matching the approach used by `nvm_print_versions`.

Bug introduced in https://github.com/nvm-sh/nvm/commit/35212c134652197c779dffd42b9567a270355987.