Add --exclude-snapshots option, which makes exclude pg_logical/snapshots

[harukat]

If there are many large file size temporary files or logical replication snapshot files in the database cluster directory, it will take longer to get a full backup. These files are not likely to be used after the restore. Therefore, I have added an option to exclude these files when obtaining full backups.

Since pg_basebackup always excludes pgsql_tmp, it is possible to always exclude pgsql_tmp and make only snapshots optional. Please let us know what you think.

[harukat]

It was pointed out to me that pgsql_tmp is already excluded in the current code, so I'll fixed it.