Added support for dynamic imports

[cgalvan]

Description

Added support for dynamic imports https://developers.google.com/maps/documentation/javascript/load-maps-js-api#dynamic-library-import

This is the recommended workflow for importing the Google API.

• Updated our adapter to support dynamic imports by providing the importLibrary method that returns a Promise to fulfill the requested library
• Added support for importing all of our currently supported classes through dynamic import
• Updated our autoComplete example to show-case the dynamic import workflow
• Added unit tests to cover all dynamic imports

Testing

Ran unit tests and verified they all pass and that we retain 100% coverage on the index.ts module

------------------|---------|----------|---------|---------|--------------------------
File              | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
------------------|---------|----------|---------|---------|--------------------------
All files         |    84.2 |    86.02 |   82.35 |   84.25 |
 directions.ts    |    9.25 |        0 |       0 |    7.69 | 26-204
 google.maps.d.ts |       0 |        0 |       0 |       0 |
 googleCommon.ts  |     100 |      100 |     100 |     100 |
 index.ts         |     100 |      100 |     100 |     100 |
 infoWindow.ts    |     100 |      100 |     100 |     100 |
 maps.ts          |     100 |    97.26 |     100 |     100 | 105
 markers.ts       |   78.66 |    66.66 |      90 |   78.66 | 63-68,88-115,140,310-334
 places.ts        |   81.19 |       84 |      75 |   81.03 | 230-278
------------------|---------|----------|---------|---------|--------------------------

Test Suites: 6 passed, 6 total
Tests:       113 passed, 113 total

Also built/ran our examples and verified they still work as expected (particularly the autoComplete example, that was changed to use the dynamic imports for both migration and google version).

[jonayuan]

Looks good to me!