Reimplement callables using `func call`. (#24122)
* Revert "[TF] Introduce callables. (#24086)"
This reverts commit f7c7edfc52627a516002d955f6cd55de2b0e305f.
* Revert "Fix `call` declaration serialization. (#24121)"
This reverts commit 6466a84d637607f2c29aeadd6dfa57ef6c3b58c8.
* Reimplement callables using `func call`.
Remove `call` declarations.
Treat methods named `func call` as call-syntax delegate methods.
