Re: Continue work on changes to recovery.conf API

Hello

Current patch moves recovery.conf settings into GUC system:
- if startup process found recovery.conf - it throw error
- recovery mode is turned on if new special file recovery.signal found
- standby_mode setting was removed. Standby mode can be enabled if startup found new special file standby.signal
- if present both standby.signal and recovery.signal - we use standby mode
(this design from previous thread)
- recovery parameters recovery_target_inclusive, recovery_target_timeline, recovery_target_action are new GUC without logic changes
- recovery_target (immediate), recovery_target_name, recovery_target_time, recovery_target_xid, recovery_target_lsn are replaced to recovery_target_type and recovery_target_value (was discussed and changed in previous thread)
- restore_command, archive_cleanup_command, recovery_end_command, primary_conninfo, primary_slot_name and recovery_min_apply_delay are just new GUC
- trigger_file was renamed to promote_signal_file for clarify (my change, in prev thread was removed)
- all new GUC are PGC_POSTMASTER (discussed in prev thread)
- pg_basebackup with -R (--write-recovery-conf) option will create standby.signal file and append primary_conninfo and primary_slot_name (if was used) to postgresql.auto.conf instead of writing new recovery.conf
- appropriate changes in tests and docs

regards, Sergei