eclean: limit keep_binpkgs lifetime to the current binrepo

This makes eclean-pkg operate on a per-binrepo basis in --unique-use
mode and fixes a KeyError caused by cross-binrepo queries.

Currently, keep_binpkgs persists across binrepos and may retain binary
packages that do not belong to the current binrepo.

When --unique-use is enabled, bin_dbapi.aux_get may then attempt to
query BUILD_TIME for a package from a different binrepo. Since bin_dbapi
only contains data for the current binrepo, it results in a KeyError.

For example, while processing libevdev-1.13.6-7 it may try to query
libevdev-1.13.6-6 from a different binrepo:

```
$ ls /var/cache/binpkgs/dev-libs/libevdev/
libevdev-1.13.6-6.gpkg.tar

$ ls /var/cache/binhost/gentoo/dev-libs/libevdev/
libevdev-1.13.6-7.gpkg.tar

$ sudo eclean-pkg --unique-use --changed-deps
...
KeyError: ('dev-libs/libevdev-1.13.6', 6, ...)
```

All users of keep_binpkgs lie in `for cpv in bin_dbapi.cpv_all()`-loop
so move its initializer right before the loop starts.

Signed-off-by: moexiami <taopyxxm@gmail.com>
Part-of: https://codeberg.org/gentoo/gentoolkit/pulls/8
Merges: https://codeberg.org/gentoo/gentoolkit/pulls/8
Signed-off-by: Sam James <sam@gentoo.org>

Author: moexiami

pym/gentoolkit/eclean/search.py

@@ -734,7 +734,6 @@ def findPackages(
     # Dictionary of binary packages to clean. Organized as
     # { location -> { cpv~build-id -> (binpkg, debugpack) } }
     dead_binpkgs: dict[str, dict[str, tuple[str, str | None]]] = {}
-    keep_binpkgs = {}
 
     def mk_binpkg_key(cpv):
         if cpv.build_id is None:
@@ -766,6 +765,7 @@ def mk_binpkg_key(cpv):
             populate_kwargs["invalid_errors"] = False
         if "force_reindex" in signature(bin_dbapi.bintree.populate).parameters:
             bin_dbapi.bintree.populate(force_reindex=True, **populate_kwargs)
+        keep_binpkgs = {}
         for cpv in bin_dbapi.cpv_all():
             cp = portage.cpv_getkey(cpv)
             binpkg_key = mk_binpkg_key(cpv)