v3.20.1

ModelingToolkit v3.20.1

Diff since v3.20.0

Closed issues:

• Build function allocating on large expressions? (#551)
• flatten could work in this case, but does not (#578)
• eval(build_function): invalid named tuple field name "derivative(qˍt(t), t)" (#584)

Merged pull requests:

• unflatten long operations in build_function (#581) (@shashi)
• fix #578 (#582) (@shashi)
• More modelingtoolkitize tests and fix mtkitize with tuples (#596) (@ChrisRackauckas)