add Expr FFI for building and combining expressions

### Is your feature request related to a problem or challenge?

I am implementing C bindings for the lancedb project (see: https://github.com/lancedb/lancedb-c) and need datafusion expression FFI so that users could pass into lancedb query filters defined as datafusion expressions.
currently, I am using SQL string filters that are then translated to datafusion expressions inside the lancedb code (in rust).
this is an unnecessary step, if the user could create the datafusion expressions directly and pass them into the lkancedb C bindings.

### Describe the solution you'd like

i have a local (to lancedb-c) implementation (of some of the datafusion Expr interface) here:
https://github.com/lancedb/lancedb-c/pull/38

however:
* it is not complete
* I will have to modify it manually every time the dataframe code change
* it might be useful for other projects

### Describe alternatives you've considered

_No response_

### Additional context

_No response_