fs: fixup negative length in fs.truncate

`fs.ftruncate`, `fsPromises.truncate`, and `fsPromises.ftruncate`
all adjust negative lengths to 0 before invoking the system call.
`fs.truncate()` was the one outlier.

This "fixes" #35632 but in the
opposite direction than discussed in the issue -- specifically by
removing an EINVAL error from one function rather than adding it to
another.

Signed-off-by: James M Snell <[email protected]>
Fixes: #35632

doc/api/fs.md

@@ -406,6 +406,8 @@ try {
 If the file previously was shorter than `len` bytes, it is extended, and the
 extended part is filled with null bytes (`'\0'`):
 
+If `len` is negative then `0` will be used.
+
 #### `filehandle.utimes(atime, mtime)`
 <!-- YAML
 added: v10.0.0
@@ -2295,6 +2297,8 @@ open('temp.txt', 'r+', (err, fd) => {
 If the file previously was shorter than `len` bytes, it is extended, and the
 extended part is filled with null bytes (`'\0'`):
 
+If `len` is negative then `0` will be used.
+
 ### `fs.futimes(fd, atime, mtime, callback)`
 <!-- YAML
 added: v0.4.2

lib/fs.js

@@ -814,6 +814,7 @@ function truncate(path, len, callback) {
   }
 
   validateInteger(len, 'len');
+  len = MathMax(0, len);
   callback = maybeCallback(callback);
   fs.open(path, 'r+', (er, fd) => {
     if (er) return callback(er);