TextGrad updating multiple functions

[allenanie]

Currently, TextGrad only works well on string updates or updating a single, isolated function that does not depend on other functions. The Trace interface can sometimes specify a workflow where multiple functions have to work together (by chaining the input/output of each function). This use case is difficult to accomplish with the current verbatim implementation TextGrad.

The GreetingAgent notebook example doesn't work with TextGrad as an optimizer.

[chinganc]

@allenanie Perhaps we can have an extended version of TextGrad as the new default, while keeping the current literal translation as an old version?