Allow distinct types in `schema::custom()` #4438

Job	Run time
Rustfmt	18s
Clippy	1m 33s
Examples (examples/actix_example)	2m 29s
Init	4s
Examples (examples/axum_example)	2m 23s
Unit Test	3m 15s
Examples (examples/basic)	1m 9s
Examples (examples/graphql_example)	3m 3s
Examples (examples/jsonrpsee_example)	2m 40s
Examples (examples/poem_example)	2m 17s
Examples (examples/proxy_gluesql_example)	1m 30s
Examples (examples/rocket_example)	3m 4s
Examples (examples/rocket_okapi_example)	3m 14s
Examples (examples/salvo_example)	2m 49s
Examples (examples/seaography_example)	2m 35s
Examples (examples/tonic_example)	2m 34s
Compile MySQL (actix, native-tls)	3m 4s
Compile PostgreSQL (tokio, native-tls)	2m 53s
Compile MySQL (actix, rustls)	3m 26s
Compile PostgreSQL (tokio, rustls)	3m 8s
Compile SQLite (async-std, native-tls)	2m 51s
CLI	0s
Compile SQLite (async-std, rustls)	3m 0s
Issues Matrix	0s
Issues	0s
Postgres (14, tokio, native-tls)	7m 12s
Postgres (16, tokio, native-tls)	6m 41s
MariaDB (lts, actix, native-tls)	2m 39s
MySQL (lts, actix, native-tls)	3m 21s
MySQL (5.7, actix, native-tls)	3m 20s
SQLite (async-std, native-tls)	5m 4s
SQLite (async-std, rustls)	4m 40s
	1h 26m 16s

Provide feedback