lib: Change Iterable to Collection for truthy checks

Change parameter types from Iterable[str] to Collection[str] wherever
the parameter is tested for emptiness (if not names). This satisfies
the new truthy-iterable mypy rule, since bare Iterable values are
always truthy even when empty.

Affected files:
- Distro.py: install, delete, select, _select, _select_by_name
- rpm.py: query_packages
- suse/Distro.py: _select_by_name
- Cmd.py (secrets): _match_files, _list_template_files, etc.
- DistroContext.py: list_template_files, list_secret_paths, etc.

Assisted-by: unsloth/Qwen3.6-35B-A3B-GGUF:IQ4_NL and pi.dev 0.81.1
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/pm/rpm.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Iterable
+from typing import TYPE_CHECKING, Collection, Iterable
 
 from ..base import InputMode
 from ..Package import Package
@@ -41,7 +41,7 @@ async def run_rpm(  # export
     return result.stdout_str
 
 async def query_packages(  # export
-    names: Iterable[str] = [],
+    names: Collection[str] = [],
     ec: ExecContext | None = None,
 ) -> Iterable[Package]:
     fmt_str = (