pgpool: Feature: Wait for follow_primary completion and report

Feature: Wait for follow_primary completion and report
failure in pcp_promote_node and enhence failover script.

This commit enhances the pcp_promote_node command to wait for
the completion of the follow_primary command triggered during
failover and enhance failover script.

Add pcp_follow_primary_wait and pcp_follow_primary_succeeded
members to Req_info. The pcp worker sets pcp_follow_primary_wait
to true before initiating failover and waits until it is cleared
by the follow_primary process.

The follow_primary execution side clears pcp_follow_primary_wait
when the processing finishes, and sets pcp_follow_primary_succeeded
to false if any error occurs during execution.

If follow_primary fails, pcp_promote_node reports an ERROR instead of
returning success, allowing users to detect failures directly from the
command result.

Enhance failover.sample.sh to checkpoint on old primary node before promote.

Branch
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V4_7_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=ba0317d7d2dec2c8b1d4936a25c2a029d720c5a5

Modified Files
--------------
doc.ja/src/sgml/ref/pcp_watchdog_info.sgml | 11 ++++++++---
doc/src/sgml/ref/pcp_watchdog_info.sgml | 10 +++++++---
src/include/pcp/pcp.h | 1 +
src/include/watchdog/watchdog.h | 2 ++
src/include/watchdog/wd_commands.h | 2 ++
src/include/watchdog/wd_ipc_defines.h | 2 +-
src/include/watchdog/wd_lifecheck.h | 3 ++-
src/libs/pcp/pcp.c | 6 ++++++
src/tools/pcp/pcp_frontend_client.c | 8 +++++---
src/watchdog/watchdog.c | 13 +++++++++++++
src/watchdog/wd_commands.c | 7 +++++++
src/watchdog/wd_json_data.c | 4 +++-
src/watchdog/wd_lifecheck.c | 10 +++++++++-
13 files changed, 66 insertions(+), 13 deletions(-)