Rename the recovery-related wait events.

Rename the recovery-related wait events.

This commit renames RecoveryWalAll and RecoveryWalStream wait events to
RecoveryWalStream and RecoveryRetrieveRetryInterval, respectively,
in order to make the names and what they are more consistent. For example,
previously RecoveryWalAll was reported as a wait event while the recovery
was waiting for WAL from a stream, and which was confusing because the name
was very different from the situation where the wait actually could happen.

The names of macro variables for those wait events also are renamed
accordingly.

This commit also changes the category of RecoveryRetrieveRetryInterval to
Timeout from Activity because the wait event is reported while waiting based
on wal_retrieve_retry_interval.

Author: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, Atsushi Torikoshi
Discussion: https://postgr.es/m/124997ee-096a-5d09-d8da-2c7a57d0816e@oss.nttdata.com