Build: Various improvements to the bundle size

What does this MR do?

Relates to: #764 (closed)

• bf316023 ci: Add webpack bundle analysis

  In order to improve the performance of our GitLab UI page, we need some way to analyse the performance

• 24426ccf build(webpack): Dynamically load Example Display

  The example display component loads a lot of dependencies: js-beautify, vue-template-compiler, highlight.js and babel.

  By loading it asynchronously we are able to save a lot on the initial load. Additionally we only load the syntax highlighting for html, css and javascript in order to save a lot of unnecessary JS.

• f7ccc1b7 build(webpack): Ensure that we only load one version of bootstrap-vue

• 6f72da76 build(webpack): Don't load moment locale files

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
• If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• If the MR changes a component's API, integration MR(s) have been opened in the following projects to ensure that the @gitlab/ui package can be upgraded quickly after the changes are released:
  • GitLab: mr_url
  • Customers Portal: mr_url
  • Status Page: mr_url
• Added the ~"component:*" label(s) if applicable.