tests

Add exists method to PaginatorTrait with tests #4852

Job	Run time
Clippy	37s
Unit Test	3m 40s
Init	4s
Rustfmt	18s
Examples (examples/axum_example)	2m 21s
Examples (examples/basic)	1m 18s
Examples (examples/actix_example)	2m 26s
Examples (examples/graphql_example)	2m 50s
Examples (examples/jsonrpsee_example)	2m 23s
Examples (examples/loco_seaography)	4m 17s
Examples (examples/loco_starter)	3m 33s
Examples (examples/react_admin)	5m 34s
Examples (examples/proxy_gluesql_example)	1m 57s
Examples (examples/rocket_example)	3m 5s
Examples (examples/loco_example)	3m 19s
Examples (examples/poem_example)	2m 27s
Examples (examples/tonic_example)	2m 33s
Examples (examples/rocket_okapi_example)	3m 13s
Examples (examples/seaography_example)	3m 2s
Examples (examples/salvo_example)	2m 49s
Compile MySQL (actix, native-tls)	2m 27s
Compile PostgreSQL (tokio, rustls)	2m 51s
Compile PostgreSQL (tokio, native-tls)	2m 43s
Compile SQLite (async-std, rustls)	2m 36s
Compile SQLite (async-std, native-tls)	2m 29s
CLI	0s
Compile MySQL (actix, rustls)	2m 46s
Issues Matrix	-1s
Issues	-1s
Postgres (16, tokio, native-tls)	4m 39s
Postgres (14, tokio, native-tls)	4m 38s
MySQL (lts, actix, native-tls)	3m 41s
MySQL (5.7, actix, native-tls)	3m 20s
MariaDB (lts, actix, native-tls)	3m 13s
SQLite (async-std, rustls)	3m 50s
SQLite (async-std, native-tls)	3m 49s
	1h 34m 46s

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