Refactor: split pages/installed_package.rs into submodules

Move the page's sub-components into pages/installed_package/:
content.rs (InstalledPackageContent), entries.rs (EntriesToolbar,
EntriesFilter, EntryRow), status_banner.rs (StatusBanner), and
toolbar.rs (build_toolbar_actions). The page root stays in the
parent module; the pages API is unchanged.

Satisfy clippy::needless_pass_by_value on the now-pub(super)
components by consuming props: EntryRow destructures EntryData and
StatusBanner takes ownership of namespace and origin_host, dropping
several clones. StatusBanner keeps one documented allow for status,
which is only pattern-matched against literals.

Author: fiskus