Workpad shows up empty and full of invalid expressions only in IE11

[bhavyarm]

Kibana version: 6.x latest snapshot

Browser version: IE11

Describe the bug: Workpad shows up with invalid expressions on IE11.

Steps to reproduce:

1. Load the sample flight data and sample data workpad from here: https://github.com/alexfrancoeur/kibana_canvas_examples
2. Open the workpad in IE11
3. Workpad shows up with invalid expressions
4. Workpad looks fine in firefox/chrome/safari

No console error in IE dev tools

Screenshots (if relevant):

[bhavyarm]

Same error with sample log data and the log data workpad from Alex's example:

[marius-dr]

Same for me on 6.x and on Master. Looks fine in Firefox.

[cqliu1]

This is probably shares the same root issue as #23548 and may be related to #23287. It looks like the Canvas plugins weren't built before the workpad loaded.

[w33ble]

Confirmed, and captured this error message:

Also, pretty sure we just fixed this in #23301. I'll confirm once I get that reviewed. And I agree with Catherine, pretty sure #23548 is the same error.

[w33ble]

I can confirm that #23301 does indeed fix the error I was seeing in the console, but Canvas still does not load in IE11 😢. Nothing shows up in the console, the network stack looks OK, but nothing ever renders.

[cqliu1]

I discussed the IE compatibility issues with @clintandrewhall, and he discovered that the issue is our webpack build isn't transpiling our plugins into code into ES5 that IE can handle.

I cut a branch https://github.com/elastic/kibana/tree/fix/canvas-in-ie with the changes I made to the webpack config that seemed to get some things to render in IE, but it's still not working correctly.

I'll be out next week and won't have time to work on IE issues, but I believe @clintandrewhall will continue looking at this stuff.