Remove specific encoder for `Group` and `DollarGroup`, use property name map #2731

Job	Run time
PHPUnit tests (ubuntu-20.04, 8.1, 4.4, server)	4m 29s
PHPUnit tests (ubuntu-20.04, 8.1, 4.4, server)	4m 29s
PHPUnit tests (ubuntu-20.04, 8.2, 4.4, server)	4m 18s
PHPUnit tests (ubuntu-20.04, 8.2, 4.4, server)	4m 18s
PHPUnit tests (ubuntu-20.04, 8.3, 4.4, server)	4m 35s
PHPUnit tests (ubuntu-20.04, 8.3, 4.4, server)	4m 35s
PHPUnit tests (ubuntu-20.04, 8.4, 4.4, server)	3m 32s
PHPUnit tests (ubuntu-20.04, 8.4, 4.4, server)	3m 32s
PHPUnit tests (ubuntu-20.04, 8.1, 6.0, replica_set)	5m 6s
PHPUnit tests (ubuntu-20.04, 8.1, 6.0, replica_set)	5m 6s
PHPUnit tests (ubuntu-20.04, 8.1, 6.0, sharded_cluster)	5m 24s
PHPUnit tests (ubuntu-20.04, 8.1, 6.0, sharded_cluster)	9m 22s
PHPUnit tests (ubuntu-20.04, 8.1, 5.0, server)	4m 6s
PHPUnit tests (ubuntu-20.04, 8.1, 5.0, server)	4m 6s
PHPUnit tests (ubuntu-20.04, 8.1, 4.4, replica_set)	5m 9s
PHPUnit tests (ubuntu-20.04, 8.1, 4.4, replica_set)	4m 59s
PHPUnit tests (ubuntu-20.04, 8.1, 4.4, sharded_cluster)	5m 24s
PHPUnit tests (ubuntu-20.04, 8.1, 4.4, sharded_cluster)	7m 14s
	1h 29m 44s

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