scripting tool: Use project buffers in io.open (#26425)

This PR makes `io.open` use our own implementation again, but instead of
the real filesystem, it will now use the project's to check file
metadata and perform read and writes using project buffers.

This also cleans up the `io.open` implementation by splitting it into
multiple methods, adds tests for various File I/O patterns, and fixes a
few bugs in read formats.

Release Notes:

- N/A

crates/scripting_tool/src/sandbox_preamble.lua

@@ -8,9 +8,9 @@ local sandbox = {}
 -- to our in-memory log rather than to stdout, we will delete this loop (and re-enable
 -- the I/O module being sandboxed below) to have things be sandboxed again.
 for k, v in pairs(_G) do
-  if sandbox[k] == nil then
-    sandbox[k] = v
-  end
+    if sandbox[k] == nil then
+        sandbox[k] = v
+    end
 end
 
 -- Allow access to standard libraries (safe subset)
@@ -29,24 +29,27 @@ sandbox.search = search
 sandbox.outline = outline
 
 -- Create a sandboxed version of LuaFileIO
-local io = {}
+-- local io = {};
+--
+-- For now we are using unsandboxed io
+local io = _G.io;
 
 -- File functions
 io.open = sb_io_open
 
 -- Add the sandboxed io library to the sandbox environment
--- sandbox.io = io -- Uncomment this line to re-enable sandboxed file I/O.
+sandbox.io = io
 
 -- Load the script with the sandbox environment
 local user_script_fn, err = load(user_script, nil, "t", sandbox)
 
 if not user_script_fn then
-  error("Failed to load user script: " .. tostring(err))
+    error("Failed to load user script: " .. tostring(err))
 end
 
 -- Execute the user script within the sandbox
 local success, result = pcall(user_script_fn)
 
 if not success then
-  error("Error executing user script: " .. tostring(result))
+    error("Error executing user script: " .. tostring(result))
 end