(perf) - Improve performance of simplify by removing traversal for type inference

[vigneshshanmugam]

• Yields around 1 - 1.5 seconds on average for files around 2MB. Gets better for files > 2MB

This PR handles the type information that is lost due to sequence expression transformation in Simplify plugin. It takes a different approach instead of traversing all of the identifiers for type information.

Before

pluginAlias                             time(ms) # visits time/visit(ms)
// Run 1
minify-simplify                         6090.013 278330   0.022
transform-simplify-comparison-operators 41.059   18348    0.002
// Run 2
minify-simplify                         6029.847 278330   0.022
transform-simplify-comparison-operators 46.415   18348    0.003
// Run 3
minify-simplify                         6045.218 278330   0.022
transform-simplify-comparison-operators 44.464   18348    0.002

After

// 1
minify-simplify                         4617.782 278330   0.017
transform-simplify-comparison-operators 122.181  18348    0.007
// 2
minify-simplify                         4718.766 278330   0.017
transform-simplify-comparison-operators 122.642  18348    0.007
// 3
minify-simplify                         4447.601 278330   0.016
transform-simplify-comparison-operators 127.682  18348    0.007

The type inference is based on the Babel inference.

• Only for identifiers we take the different path

[boopathi]

I'm not sure if this affects the babel-7 upgrade. I think we should test this against Babel7. What do you think?

[vigneshshanmugam]

No it stays the same, No change for babel 7

https://github.com/babel/babel/blob/64dfb7574e924be3ad737c33cbc81d619dbc14c6/packages/babel-traverse/src/path/inference/index.js#L109-L111