Flatten associative composition application and simplification

[zliu41]

In some cases, we can have complex composition operator application like ((f . g) . (h . (i. j)) which is equivalent to f . g . h . i . j, which can have some opportunity of simplification via g . h = someexp. The original form is obscure to apply such simplification. Therefore, common procedure is to apply flattening simplification to have a normal reducible form and apply further simplification.

Acceptance Criteria:

• Identify the cases where this is effective.
• Have a consensus inside the team about the approach (discussing pros and cons)
• Implement flattening and simplification if decided.

(Extricated from https://kitty-hawk.atlassian.net/browse/SW-3372)