Quoted table names containing square brackets need to be regex escaped

[aidanharan]

Fixes the failing activerecord/test/cases/relations_test.rb tests. The tests were failing because table names in the SQL Server adapter use square brackets. The table names were then being used in a regular expression without first being regex escaped causing the regex not to work as expected. This PR escapes the table name in the regex.

Table name not suitable for regex:

connection.quote_table_name(table.name) 
=> "[comments]"

Table name suitable for regex:

Regexp.escape(connection.quote_table_name(table.name))
=> "\\[comments\\]"

[aidanharan]

Just found that @lcreid has already fixed this issue in Rails #722

In this PR I've taken the method from Rails master and patched the adapter so that the relations tests pass for Rails 5.2.4.x

[lcreid]

Thanks, @aidanharan . I was going to ask that the Rails fix be back-ported, but this is much faster.