Remove use of Webpack aliases

[elasticmachine]

Original comment by @ycombinator:

Clone of LINK REDACTED applicable to the UI codebase in this (x-plugins) repo

One of the benefits of the ES6 import syntax is that it enables static analysis. Our use of webpack aliases limits the benefit by making some import paths dynamic.

I don't know what all the ramifications of this change would be, but I wanted to float the idea of removing our use of aliases.

This can be split up into a number of incremental steps:

• Replace 'ui' in import declarations with the relative path to src/ui/public - place on hold because of Remove use of 'ui' webpack alias in non-ui code #7292 (comment)
• Replace imports that rely on LINK REDACTED with explicit paths to the imported file - see Remove webpack-directory-name-as-main dependency and corresponding non-standard default module behavior #7511 for changes in OSS Kibana
• Replace plugins/${plugin.id} imports with ${plugin.directory}/public
• Repeat the same 3 steps above for require expressions (is this worth the effort? require won't gain the same static analysis benefits that import statements do, but it'll be necessary if we want to remove the aliases entirely)

[stacey-gammon]

Closing in favor of #6430