Adds a few canonicalizers, folders, and rewrite patterns to tensor ops:
* tensor.insert folder: insert into a constant is replaced with a new
constant
* tensor.extract folder: extract from a parent tensor that was inserted
at the same indices is folded into the inserted value
* rewrite pattern added that replaces an extract of a collapse shape
with an extract of the source tensor (requires static source dimensions)
Signed-off-by: Asra Ali <asraa@google.com>
34d8275e4f