Use `read` in c_binds, rather than custom buffer manipulation

[iAmMichaelConnor]

Notably, functions for computing the tree roots have serialisation errors, because we aren't using our standard read functions.

• merge the pr (fix(fns): fixed computing of function tree root aztec-packages#217) where we use a raw buffer in circuits.js for computing the root, fixing the bug and adding the test
• the circuits team can change the implementation of computing the function trees to use vectors
• we update in a PR the circuits submodule to the one that expects vectors and in the same PR we update circuits.js to pass vector instead of raw buffer in both compute fn tree and compute fn tree root, so it remains consistent and the test still passes

https://aztecprotocol.slack.com/archives/C03P17YHVK8/p1681116943920249?thread_ts=1680819637.317059&cid=C03P17YHVK8

[dbanks12]

Ticket for the ts side: AztecProtocol/aztec-packages#218