[LS] Fix WASM regression & add tests

closes #249

Description

It appears that in https://github.com/onflow/cadence-tools/pull/228, I inadvertently introduced a regression into the WASM LS & was also missing certain necessary JS changes to the WASM NPM package.

This PR does the following:

Fixes regression with only address being used for address identifiers (i.e. "0000000000000001" instead of "0000000000000001.HelloWorld")
Adds WASM integration tests into the test CI job & creates tests for each of the import resolvers
Adds the missing JS wrapper for the getStringCode resolver introduced in https://github.com/onflow/cadence-tools/pull/228

I've also manually tested both import resolvers for the WASM LS package in the Flow Playground manually.

[x] Targeted PR against master branch
[x] Linked to Github issue with discussion and accepted design OR link to spec that describes this work
[x] Code follows the standards mentioned here
[x] Updated relevant documentation
[x] Re-reviewed Files changed in the Github PR explorer
[x] Added appropriate labels

onflow / cadence-tools

[LS] Fix WASM regression & add tests #248

Description