This patch renames `seq1` and `seq2` to `input1` and `input2` in `Strip`
and `StripSelection` structs to consist with recent refactors in
#132179. It also renames other instances of `seq1` and `seq2` (e.g.
local variables) to `strip1` and `strip2` instead.
There is only one small breaking change to the Python API with
`strips.new_effect()` taking in the new names now. There should be
no other functional changes involved.
Pull Request: https://projects.blender.org/blender/blender/pulls/138296
41781df1a6