We want to be able to exclude tables from background compaction.

This ticket should:

• Create a new configuration parameter "exclude" that takes a list of tables to exclude.
• Implement the code to update that list when background compaction is enabled.
• Update the code that decides whether background compaction should skip a table by using the new list.
• Add relevant stats if necessary.
• Create tests.

Example of valid configuration:

        config = 'background=true,exclude=["table:a.wt","table:b.wt"]'

Note that only the prefix "table" should be used.

The existing backup_restore_target could be reused as an example which has already been implemented.