Simplify client wasms.

[zie1ony]

client directory has 6 crates, where 1 with 6 bins would be enough.

This could be simplified even more with general purpose caller that can handle response and store it, so for test env could read it. We have built it for Odra. You could simply copy it over here.
https://github.com/odradev/odra/blob/release/0.2.0/odra-casper/test-env/getter_proxy/bin/getter_proxy.rs#L26

[RBYGLLS]

2nd discussion on entry points need some clariity on direction : account entry points vs contract entry points