deb,build: export ddebs from binary builds

dh_strip registers debug-symbol packages in debian/files under their
renamed .ddeb name; they are deliverables of the build just like the
regular .debs. Both artifact-type filters, the one collecting the
build's artifacts and the one feeding the .buildinfo/.changes
checksum sections, accepted only deb and udeb, so every ddeb a build
produced was silently discarded: nothing exported next to the .debs,
nothing in the upload metadata.

The filter is now a shared FilesEntry::is_binary_artifact() predicate
(plus unit tests) used by both call sites, so the two cannot drift
apart again.

One dpkg distinction has to be copied rather than shared:
dpkg-genchanges lists only deb/udeb packages in the changes' Binary:
and Description (a ddeb travels in Files and the checksum sections
but is not a listed binary of the upload), while dpkg-genbuildinfo
lists every binary artifact's package, ddebs included. The package
list is therefore accumulated twice, once per consumer.

The binary-metadata differential fixture gains a Package-Type: ddeb
package, so the native .changes/.buildinfo generation is compared
against real dpkg with a ddeb present. Without the fix the comparison
fails on the checksum sections (golden distributes the ddeb, ours
dropped it); with it every field matches.

src/build/mod.rs

@@ -1889,19 +1889,22 @@ Provides: virtual-thing (= 2.0), plain-virtual
     }
 
     /// debian/control shared by the binary-metadata differential cases: one
-    /// arch:any deb and one arch:all udeb.
+    /// arch:any deb, one arch:all udeb and one arch:all ddeb (the
+    /// debug-symbol shape dh_strip leaves behind: the package type
+    /// drives the file name in debian/files).
     fn binary_test_control(name: &str) -> String {
         format!(
             "Source: {name}\nSection: utils\nPriority: optional\nMaintainer: {MAINTAINER}\nBuild-Depends: libc6\n\n\
              Package: {name}\nArchitecture: any\nDescription: test package main\n long description\n\n\
-             Package: {name}-u\nPackage-Type: udeb\nArchitecture: all\nDescription: test udeb\n short\n"
+             Package: {name}-u\nPackage-Type: udeb\nArchitecture: all\nDescription: test udeb\n short\n\n\
+             Package: {name}-d\nPackage-Type: ddeb\nArchitecture: all\nDescription: test ddeb\n short\n"
         )
     }
 
     /// debian/rules driving dpkg-gencontrol/dpkg-deb directly (no debhelper).
     fn binary_test_rules(name: &str) -> String {
         format!(
-            "#!/usr/bin/make -f\nV = $(shell dpkg-parsechangelog -S Version)\nA = $(shell dpkg-architecture -qDEB_HOST_ARCH)\n\nbuild:\n\tmkdir -p debian/tmp/usr/bin\n\tprintf '#!/bin/sh\\necho hi\\n' > debian/tmp/usr/bin/hello\n\tchmod 755 debian/tmp/usr/bin/hello\n\ttouch $@\n\nbinary: build\n\trm -rf debian/{name} debian/{name}-u\n\tmkdir -p debian/{name}/usr/bin debian/{name}/DEBIAN\n\tcp -r debian/tmp/. debian/{name}/\n\tdpkg-gencontrol -p{name} -Pdebian/{name}\n\tdpkg-deb --build debian/{name} ..\n\tmkdir -p debian/{name}-u/usr/share debian/{name}-u/DEBIAN\n\techo data > debian/{name}-u/usr/share/data.txt\n\tdpkg-gencontrol -p{name}-u -Pdebian/{name}-u\n\tdpkg-deb --build debian/{name}-u ..\n\tmv ../{name}-u_$(V)_all.deb ../{name}-u_$(V)_all.udeb\n\nclean:\n\trm -rf debian/tmp debian/{name} debian/{name}-u build-stamp debian/files debian/*.substvars\n\n.PHONY: build binary clean\n"
+            "#!/usr/bin/make -f\nV = $(shell dpkg-parsechangelog -S Version)\nA = $(shell dpkg-architecture -qDEB_HOST_ARCH)\n\nbuild:\n\tmkdir -p debian/tmp/usr/bin\n\tprintf '#!/bin/sh\\necho hi\\n' > debian/tmp/usr/bin/hello\n\tchmod 755 debian/tmp/usr/bin/hello\n\ttouch $@\n\nbinary: build\n\trm -rf debian/{name} debian/{name}-u debian/{name}-d\n\tmkdir -p debian/{name}/usr/bin debian/{name}/DEBIAN\n\tcp -r debian/tmp/. debian/{name}/\n\tdpkg-gencontrol -p{name} -Pdebian/{name}\n\tdpkg-deb --build debian/{name} ..\n\tmkdir -p debian/{name}-u/usr/share debian/{name}-u/DEBIAN\n\techo data > debian/{name}-u/usr/share/data.txt\n\tdpkg-gencontrol -p{name}-u -Pdebian/{name}-u\n\tdpkg-deb --build debian/{name}-u ..\n\tmv ../{name}-u_$(V)_all.deb ../{name}-u_$(V)_all.udeb\n\tmkdir -p debian/{name}-d/usr/share debian/{name}-d/DEBIAN\n\techo data > debian/{name}-d/usr/share/data.txt\n\tdpkg-gencontrol -p{name}-d -Pdebian/{name}-d\n\tdpkg-deb --build debian/{name}-d ..\n\tmv ../{name}-d_$(V)_all.deb ../{name}-d_$(V)_all.ddeb\n\nclean:\n\trm -rf debian/tmp debian/{name} debian/{name}-u debian/{name}-d build-stamp debian/files debian/*.substvars\n\n.PHONY: build binary clean\n"
         )
     }