tfhe_rust: improve generality of e2e test runner

[j2kun]

• Support generated functions with multiple return values
• Support a variable number of input arguments (not just 2 ints)
• Custom function name besides fn_under_test?

[j2kun]

Variadic args seems hard in rust because rust doesn't have a splat operator to read in the variadic CLI arguments and convert them to a static function signature. I thought maybe macro_rules would provide a workaround, but didn't have the time to figure it out.

[j2kun]

A colleague pointed me to this which might help support the variadic arguments issue: https://jsdw.me/posts/rust-fn-traits/

See the section "Accepting variable arity functions using Trait Families"

[github-actions[bot]]

This issue has 4 outstanding TODOs:

• tests/Examples/tfhe_rust/src/main.rs:6: improve generality
• tests/Examples/tfhe_rust/src/main_add_one.rs:7: improve generality
• tests/Examples/tfhe_rust/src/main_fully_connected.rs:9: improve generality
• tests/Examples/tfhe_rust_bool/fpga/src/main_fully_connected.rs:13: improve generality

This comment was autogenerated by todo-backlinks

[j2kun]

Now that I've got the openfhe e2e tests working, it seems reasonable to migrate to proper rust rules and a rust test harness instead of lit testing.