🏗✨ Upgrade closure compiler to v20190513

[rsimha]

This PR upgrades the version of closure compiler used to minify the AMP runtime to v20190513.

Highlights:

• Updated compiler.jar with a custom built version based on v20190513
  • Reverts two breaking changes in closure compiler code (one, two) (required until ES6 module support for "type-only import" like goog.requireType or TS import type google/closure-compiler#3041 is fixed)
• Updated compiler-and-tests.jar with a custom built version based on v20190513
  • Follows the steps outlined here
• Updated documentation for custom build changes in README.amp
• Updated runner.jar after fixing code and tests to be compatible with latest compiler code
• Fixed a few type check errors discovered by the new version
• Adopted the recently introduced @closurePrimitive annotations for assertion functions
• Removed the getAssertionFunctions() override in AmpCodingConvention.java

Future work: Dynamically generate runner.jar once we no longer need a custom built compiler.jar (#22452)

Companion to #22368
Partial fix for #18748
Follow up to #18552, #18609, #18794, #19449, #20056, and #21618

[rsimha]

Tested this as follows:

• Minified build is green (link)
• Type checker is green (link)
• Running time for gulp dist is unaffected (link)
• Zero visual diffs (link)
• Single pass build and tests are green (link)
• Local and remote tests all green (link, link)
• Size of v0.js and number of instances of the string assert remain unchanged with 2a45d76
• Manually sanity checked the runtime + extensions in multi pass and single pass modes
• Source maps continue to work with this verification tool