Add Linalg pattern for producer-consumer fusion

This CL adds a simple pattern for specifying producer-consumer fusion on Linalg operations.

Implementing such an extension reveals some interesting properties.
Since Linalg operates on a buffer abstraction, the output buffers are specified as in/out parameters to the ops. As a consequence, there are no SSA use-def chains and one cannot specify complex dag input patterns with the current infrastructure.

Instead this CL uses constraints based on the existing linalg dependence analysis to focus the pattern and refine patterns based on the type of op that last wrote in a buffer.

This is a very local property and is less powerful than the generic dag specification based on SSA use-def chains.

This will be generalized in the future.

PiperOrigin-RevId: 277931503