refactor: delete `Caller` trait #5698

Job	Run time
wasm-wasi	1m 40s
test ubuntu-latest stable --no-default-features	2m 11s
feature-checks	4m 32s
doctest	2m 6s
wasm-unknown	1m 9s
test ubuntu-latest stable	2m 6s
check no_std	17s
clippy	48s
test ubuntu-latest stable --all-features	2m 42s
test ubuntu-latest nightly --no-default-features	1m 18s
docs	1m 8s
fmt	13s
test ubuntu-latest nightly	1m 33s
test ubuntu-latest nightly --all-features	2m 14s
test ubuntu-latest 1.81 --no-default-features	1m 10s
test ubuntu-latest 1.81	1m 22s
test windows-latest stable --no-default-features	5m 5s
test windows-latest stable	5m 26s
test windows-latest stable --all-features	6m 31s
test windows-latest nightly --no-default-features	4m 49s
test windows-latest nightly	4m 8s
test windows-latest nightly --all-features	6m 15s
test windows-latest 1.81 --no-default-features	3m 14s
test windows-latest 1.81	2m 52s
deny / cargo deny check	21s
ci success	3s
	1h 5m 13s

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