service/fsp_srv: Implement CleanDirectoryRecursively

This is the same behavior-wise as DeleteDirectoryRecursively, with the
only difference being that it doesn't delete the top level directory in
the hierarchy, so given:

root_dir/
  - some_dir/
    - File.txt
  - OtherFile.txt

The end result is just:

root_dir/

2 files changed, 37 insertions, 4 deletions

diff --git a/src/core/file_sys/vfs.cpp b/src/core/file_sys/vfs.cpp
index 7b584de7f..a4a3236f4 100644
--- a/src/core/file_sys/vfs.cpp
+++ b/src/core/file_sys/vfs.cpp
@@ -384,6 +384,28 @@ bool VfsDirectory::DeleteSubdirectoryRecursive(std::string_view name) {
     return success;
 }
 
+bool VfsDirectory::CleanSubdirectoryRecursive(std::string_view name) {
+    auto dir = GetSubdirectory(name);
+    if (dir == nullptr) {
+        return false;
+    }
+
+    bool success = true;
+    for (const auto& file : dir->GetFiles()) {
+        if (!dir->DeleteFile(file->GetName())) {
+            success = false;
+        }
+    }
+
+    for (const auto& sdir : dir->GetSubdirectories()) {
+        if (!dir->DeleteSubdirectoryRecursive(sdir->GetName())) {
+            success = false;
+        }
+    }
+
+    return success;
+}
+
 bool VfsDirectory::Copy(std::string_view src, std::string_view dest) {
     const auto f1 = GetFile(src);
     auto f2 = CreateFile(dest);
@@ -435,6 +457,10 @@ bool ReadOnlyVfsDirectory::DeleteSubdirectory(std::string_view name) {
     return false;
 }
 
+bool ReadOnlyVfsDirectory::CleanSubdirectoryRecursive(std::string_view name) {
+    return false;
+}
+
 bool ReadOnlyVfsDirectory::DeleteFile(std::string_view name) {
     return false;
 }
diff --git a/src/core/file_sys/vfs.h b/src/core/file_sys/vfs.h
index 002f99d4e..6e1db36f1 100644
--- a/src/core/file_sys/vfs.h
+++ b/src/core/file_sys/vfs.h
@@ -245,12 +245,18 @@ public:
     // any failure.
     virtual std::shared_ptr<VfsDirectory> CreateDirectoryAbsolute(std::string_view path);
 
-    // Deletes the subdirectory with name and returns true on success.
+    // Deletes the subdirectory with the given name and returns true on success.
     virtual bool DeleteSubdirectory(std::string_view name) = 0;
-    // Deletes all subdirectories and files of subdirectory with name recirsively and then deletes
-    // the subdirectory. Returns true on success.
+
+    // Deletes all subdirectories and files within the provided directory and then deletes
+    // the directory itself. Returns true on success.
     virtual bool DeleteSubdirectoryRecursive(std::string_view name);
-    // Returnes whether or not the file with name name was deleted successfully.
+
+    // Deletes all subdirectories and files within the provided directory.
+    // Unlike DeleteSubdirectoryRecursive, this does not delete the provided directory.
+    virtual bool CleanSubdirectoryRecursive(std::string_view name);
+
+    // Returns whether or not the file with name name was deleted successfully.
     virtual bool DeleteFile(std::string_view name) = 0;
 
     // Returns whether or not this directory was renamed to name.
@@ -277,6 +283,7 @@ public:
     std::shared_ptr<VfsDirectory> CreateSubdirectory(std::string_view name) override;
     std::shared_ptr<VfsFile> CreateFile(std::string_view name) override;
     bool DeleteSubdirectory(std::string_view name) override;
+    bool CleanSubdirectoryRecursive(std::string_view name) override;
     bool DeleteFile(std::string_view name) override;
     bool Rename(std::string_view name) override;
 };