Add Read-only Transaction check to function calls

[yiyun-sj]

At client_context.cpp:320-331 we check if a statement would be a valid read-only statement for read-only transactions. However, the expressions within the statements could contain functions that could perform a write. We currently don't check this. As well, we don't seem to check if macro functions are read-only either. We perhaps want to handle this in the binding stage instead of the parser stage as above.

[ray6080]

We should introduce a more scalable infrastructure to track if a statement/expression/function is modifying the database or not (perhaps during binder phase). @andyfengHKU or @acquamarin should take a look at this.