derive: unify filter argument handling #1001

Job	Run time
Rustfmt	11s
Audit	16s
Docs (rinja)	22s
Check order in Cargo.toml	7s
Docs (rinja_derive)	19s
DevSkim	33s
Book	6s
Docs (rinja_parser)	13s
Jinja2-Assumptions	16s
Typos	22s
MSRV	21s
Test (ubuntu-latest, stable)	42s
Test (ubuntu-latest, beta)	52s
Test (macos-latest, stable)	44s
Test (windows-latest, stable)	2m 37s
Package (examples/actix-web-app)	51s
Package (examples/axum-app)	38s
Package (examples/poem-app)	55s
Package (examples/rocket-app)	1m 12s
Package (examples/salvo-app)	1m 1s
Package (examples/warp-app)	59s
Package (fuzzing)	33s
Package (rinja)	29s
Package (rinja_derive)	21s
Package (rinja_derive_standalone)	34s
Package (rinja_parser)	30s
Package (testing)	1m 0s
Package (testing-alloc)	19s
Package (testing-no-std)	16s
Cluster-Fuzz	14m 11s
Fuzz (all)	5m 9s
Fuzz (filters)	5m 15s
Fuzz (html)	5m 11s
Fuzz (parser)	5m 24s
	52m 49s

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