feat: add Query Builder `explain()` #15206

Job	Run time
Setup PHP Version for Code Coverage	4s
Others (8.2) / Sanity Tests	3m 10s
Others (8.5) / Sanity Tests	1m 46s
Others (8.4) / Sanity Tests	1m 29s
Others (8.3) / Sanity Tests	1m 32s
CacheLive (8.5) / Cache Live Tests	1m 28s
CacheLive (8.3) / Cache Live Tests	1m 27s
CacheLive (8.2) / Cache Live Tests	1m 45s
CacheLive (8.4) / Cache Live Tests	1m 27s
SeparateProcess (8.4) / tests	2m 2s
SeparateProcess (8.3) / tests	2m 6s
SeparateProcess (8.2) / tests	2m 1s
SeparateProcess (8.5) / tests	2m 9s
DatabaseLive (8.5, Postgre, 8.0) / tests	2m 2s
DatabaseLive (8.2, Postgre, 8.0) / tests	2m 40s
DatabaseLive (8.5, SQLite3, 8.0) / tests	1m 6s
DatabaseLive (8.5, MySQLi, 8.0) / tests	3m 57s
DatabaseLive (8.5, OCI8, 8.0) / tests	7m 34s
DatabaseLive (8.2, SQLite3, 8.0) / tests	2m 8s
DatabaseLive (8.3, OCI8, 8.0) / tests	7m 48s
DatabaseLive (8.2, SQLSRV, 8.0) / tests	10m 56s
DatabaseLive (8.2, MySQLi, 5.7) / tests	3m 37s
DatabaseLive (8.4, OCI8, 8.0) / tests	8m 5s
DatabaseLive (8.3, SQLSRV, 8.0) / tests	5m 45s
DatabaseLive (8.2, OCI8, 8.0) / tests	10m 4s
DatabaseLive (8.4, MySQLi, 8.0) / tests	3m 15s
DatabaseLive (8.3, Postgre, 8.0) / tests	1m 39s
DatabaseLive (8.3, MySQLi, 8.0) / tests	3m 55s
DatabaseLive (8.5, SQLSRV, 8.0) / tests	4m 47s
DatabaseLive (8.4, Postgre, 8.0) / tests	1m 39s
DatabaseLive (8.3, SQLite3, 8.0) / tests	1m 22s
DatabaseLive (8.4, SQLSRV, 8.0) / tests	5m 4s
DatabaseLive (8.2, MySQLi, 8.0) / tests	5m 4s
DatabaseLive (8.4, SQLite3, 8.0) / tests	1m 2s
Upload coverage results to Coveralls / coveralls	51s
	1h 56m 46s

Provide feedback