Bug#57154 Rename THREADS.ID to THREADS.PROCESSLIST_ID in 5.5

This change is to align the 5.5 performance_schema.THREADS
table definition with the 5.6 performance_schema.THREADS table,
to facilitate the 5.5 -> 5.6 migration later.

In the table performance_schema.THREADS:
- renamed ID to PROCESSLIST_ID, removed not null
- changed NAME from varchar(64) to varchar(128)
to match the columns definitions from 5.6

Adjusted the test cases accordingly.

Note: this fix is for 5.5 only, to null merge into 5.6

storage/perfschema/table_threads.h

@@ -36,7 +36,7 @@ struct row_threads
 {
   /** Column THREAD_ID. */
   ulong m_thread_internal_id;
-  /** Column ID. */
+  /** Column PROCESSLIST_ID. */
   ulong m_thread_id;
   /** Column NAME. */
   const char *m_name;
@@ -79,7 +79,7 @@ private:
 
   /** Current row. */
   row_threads m_row;
-  /** True is the current row exists. */
+  /** True if the current row exists. */
   bool m_row_exists;
   /** Current position. */
   PFS_simple_index m_pos;