Media: Store attachment’s file size in metadata.

Store the file size of all newly uploaded attachments, as part of the metadata stored in post meta. Storing file size means, developers will not have to resort to doing `filesize` function calls, that can be time consuming on assets on offloaded to services like Amazon’s S3. 

This change also introduces a new helper function called, `wp_filesize`. This is a wrapper around the `filesize` php function, that adds some helpful filters and ensures the return value is an integer.

Props Cybr, Spacedmonkey, SergeyBiryukov, johnwatkins0, swissspidy, desrosj, joemcgill, azaozz, antpb, adamsilverstein, uday17035. 
Fixes #49412. 



git-svn-id: https://develop.svn.wordpress.org/trunk@52837 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/file.php

@@ -2555,3 +2555,41 @@ function wp_opcache_invalidate( $filepath, $force = false ) {
 
 	return false;
 }
+
+/**
+ * Wrapper for PHP filesize with filters and casting the result as an integer.
+ *
+ * @since 6.0.0
+ *
+ * @link https://www.php.net/manual/en/function.filesize.php
+ *
+ * @param string $path Path to the file.
+ * @return int The size of the file in bytes, or 0 in the event of an error.
+ */
+function wp_filesize( $path ) {
+	/**
+	 * Filters the result of wp_filesize before the PHP function is run.
+	 *
+	 * @since 6.0.0
+	 *
+	 * @param null|int $size The unfiltered value. Returning an int from the callback bypasses the filesize call.
+	 * @param string   $path Path to the file.
+	 */
+	$size = apply_filters( 'pre_wp_filesize', null, $path );
+
+	if ( is_int( $size ) ) {
+		return $size;
+	}
+
+	$size = (int) @filesize( $path );
+
+	/**
+	 * Filters the size of the file.
+	 *
+	 * @since 6.0.0
+	 *
+	 * @param int    $size The result of PHP filesize on the file.
+	 * @param string $path Path to the file.
+	 */
+	return (int) apply_filters( 'wp_filesize', $size, $path );
+}