feat: add parameter pg_fs_wal (G) to changing pg_wal dir

[waitingsong]

new pg_wal style is <pg_fs_wal>/<pg_cluster>-<pg_version>/pg_wal when pg_fs_wal defined

pg_fs_wal validatiton: pg_fs_wal must start with '/' and not contain spaces

modify pg_wal of current pg_cluster:

1. edit and save pigsty.yml by setting the global pg_wal
2. run command ./pgsql.yml - <cls> -t pg_wal

tested scenarios:

• pig sty install
  • pg_fs_wal undefined
  • pg_fs_wal defined
• bin/pgsql-add <pg_cluster>
  • pg_fs_wal undefined
  • pg_fs_wal defined
• bin/pgsql-add <pg_cluster> <ip>
• ./pgsql.yml -t pg_wal after full installation
  • set pg_fs_wal=/wal
  • set pg_fs_wal=/wal2 (from /wal)
  • remove pg_fs_wal (from /wal2)
• multiple call ./pgsql.yml -t pg_wal
  • keep pg_fs_wal undefined or blank
  • keep pg_fs_wal=/wal

pg-backup full will be executed automatically if pg_fs_wal changed and apply this settings:

• full installation with valid pg_fs_wal (no backup operation if pg_fs_wal undefined or blank)
• pg_fs_wal changed after installation
  • undefined or empty to /wal
  • /wal to /wal2
  • /wal2 to undefined or empty