Tee/teeWith seem to have a fusion issue

[harendra-kumar]

We observed in the streamly-statistics package that some benchmarks with Tee take a lot of time and the fusion-plugin also takes a long time and large amount of memory to build those benchmarks. For this reason we have not been able to test whether they would fuse with fusion-plugin.

This needs to be investigated further.

[harendra-kumar]

Looks like the issue occurs when there is a nesting of a Tee inside another Tee.

[harendra-kumar]

For flat structure amenable to fusion we need Tee3, Tee4 etc. to distribute input to 3 or 4 folds respectively.