Add Cordova support to the compatibility layer

[sam-gc]

This change adds Cordova support to the compat package by dynamically choosing which resolver to use at runtime. In order to get this to work, I had to change the Cordova plugin types to be declared as an interface extending Window instead of passive declare namespace. Honestly this is probably for the better because that's broken like half the time

[google-oss-bot]

Binary Size Report

Affected SDKs

No changes between base commit (d4ba8da) and head commit (e2c5fe1).

Test Logs

• Base (d4ba8daa): https://github.com/firebase/firebase-js-sdk/actions/runs/600594116
• Head (e2c5fe1c): https://github.com/firebase/firebase-js-sdk/actions/runs/600698477

[google-oss-bot]

Size Analysis Report

Affected Products

No changes between base commit (d4ba8da) and head commit (e2c5fe1).

Test Logs

• Base (d4ba8da): https://github.com/firebase/firebase-js-sdk/actions/runs/600594116
• Head (e2c5fe1): https://github.com/firebase/firebase-js-sdk/actions/runs/600698477