feat: add Query Builder `explain()` #15214

Job	Run time
Setup PHP Version for Code Coverage	4s
Others (8.4) / Sanity Tests	1m 43s
Others (8.2) / Sanity Tests	3m 22s
Others (8.3) / Sanity Tests	1m 29s
Others (8.5) / Sanity Tests	1m 34s
SeparateProcess (8.3) / tests	2m 14s
SeparateProcess (8.5) / tests	2m 3s
SeparateProcess (8.4) / tests	2m 15s
SeparateProcess (8.2) / tests	2m 15s
CacheLive (8.2) / Cache Live Tests	1m 47s
CacheLive (8.3) / Cache Live Tests	1m 32s
DatabaseLive (8.2, OCI8, 8.0) / tests	10m 56s
CacheLive (8.4) / Cache Live Tests	1m 39s
DatabaseLive (8.4, MySQLi, 8.0) / tests	3m 58s
DatabaseLive (8.3, MySQLi, 8.0) / tests	6m 37s
DatabaseLive (8.2, MySQLi, 8.0) / tests	4m 25s
DatabaseLive (8.4, OCI8, 8.0) / tests	12m 8s
DatabaseLive (8.4, Postgre, 8.0) / tests	1m 57s
CacheLive (8.5) / Cache Live Tests	1m 35s
DatabaseLive (8.2, Postgre, 8.0) / tests	2m 45s
DatabaseLive (8.5, SQLSRV, 8.0) / tests	5m 0s
DatabaseLive (8.4, SQLite3, 8.0) / tests	1m 16s
DatabaseLive (8.2, MySQLi, 5.7) / tests	3m 25s
DatabaseLive (8.3, Postgre, 8.0) / tests	1m 42s
DatabaseLive (8.2, SQLSRV, 8.0) / tests	7m 21s
DatabaseLive (8.4, SQLSRV, 8.0) / tests	4m 58s
DatabaseLive (8.3, SQLite3, 8.0) / tests	1m 3s
DatabaseLive (8.5, OCI8, 8.0) / tests	8m 27s
DatabaseLive (8.2, SQLite3, 8.0) / tests	2m 10s
DatabaseLive (8.3, SQLSRV, 8.0) / tests	5m 28s
DatabaseLive (8.5, MySQLi, 8.0) / tests	3m 9s
DatabaseLive (8.3, OCI8, 8.0) / tests	7m 40s
DatabaseLive (8.5, SQLite3, 8.0) / tests	1m 9s
DatabaseLive (8.5, Postgre, 8.0) / tests	1m 40s
Upload coverage results to Coveralls / coveralls	46s
	2h 1m 32s

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