[Installer] Name only the payload programs installed in the directory (#7684)

The running-instance lookup named every process whose image path began with the
install directory, subfolders included. Installing into a folder that holds
another application in a subfolder therefore reported that application as
holding the previous version, and nothing the guard offers could clear it: the
close asks cockatrice.exe only, and the end answer refuses anything that is not
a payload program. Both answers were no-ops, so the update could only abort and
tell the user to close a program that was never touching the files.

Name only the programs the payload installs, and only when the image lies in the
install directory itself. A program below the directory that really does hold a
payload file is still named by the Restart Manager lookup, which is the lookup
for that question.

The Windows probe check now covers a payload-named program in a subfolder and a
program the payload does not install; both have to come back as nothing.

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

tools/installer-holder-probe/payload_paths.h

@@ -0,0 +1,39 @@
+#ifndef PAYLOAD_PATHS_H
+#define PAYLOAD_PATHS_H
+
+#include <string>
+
+/**
+ * @brief The last name in @p path: what follows its last separator, or @p path itself when
+ *        it has none.
+ *
+ * Empty for an empty path and for one that ends in a separator, which has no name of its
+ * own - a caller that hands in a directory there gets no name rather than the directory's
+ * own last component.
+ */
+std::wstring fileNameOf(const std::wstring &path);
+
+/**
+ * @brief The directory @p path lies in, without a trailing separator.
+ *
+ * Empty when @p path has no directory part. Used to tell where a process was started from:
+ * an image running directly in the install directory has that directory as its parent,
+ * while one started from a folder below it has that folder, and the two are not the same
+ * answer to "does this process belong to the installation being replaced?".
+ */
+std::wstring parentDirectoryOf(const std::wstring &path);
+
+/**
+ * @brief Whether @p imageName is one of the programs the payload installs.
+ *
+ * The single place that answers which images are Cockatrice's own, so the guard acts on the
+ * same set it names, and so a program a user happens to keep in the install directory is
+ * never treated as an instance of the application. Matched on the image name alone, without
+ * case: the names are the payload's own, and the comparison is deliberately free of Windows
+ * API so it can be exercised off Windows.
+ *
+ * @param imageName the file name of a process image, empty when it could not be read
+ */
+bool isPayloadProgram(const std::wstring &imageName);
+
+#endif