Escape column name in Replace Tool

As described in https://moodle.org/mod/forum/discuss.php?d=354485 sometimes plug-in developers doesn't properly care about reserved words when they design their data models: it could happen that their choices conflict for one or more DB Servers among the ones supported by Moodle.

Unfortunately this local - i.e. the plug-in can't run when Moodle uses a specific DB server - issue can reflect in those Moodle tools that play with the database tables like the Replace Tool.

To replicate:

1. Add a new column field (XMLDB_TYPE_CHAR or XMLDB_TYPE_TEXT) using a reserved word crossing the DBs like where in a core table e.g. In MySQL, by altering the scorm table w/ a new XMLDB_TYPE_CHAR field:

   ALTER TABLE mdl_scorm ADD `where` VARCHAR(20) COLLATE utf8mb4_bin DEFAULT 'localhost';

2. Try to use the Replace Tool e.g.

   php admin/tool/replace/cli/replace.php --search=//oldsitehost --replace=//newsitehost

3. Expected:
   • The replace tool will complete successfully.
4. Actual:
   • An error is encountered.