Use Azure storage SDK to download cache (#497)

* Adds option to download using AzCopy

* Bump version number and add release notes

* Ensure we use at least v10

* Negate env var so it disables AzCopy

* Use Azure storage SDK to download cache

* Use same level of parallelism as AzCopy

* Fix naming of variable

* React to feedback

* Bump Node types to Node 12

* Make linter happy

* Pass options into restoreCache method

* Fix tests

* Restructure files and add tests

* Add method to get the default download and upload options

* Include breaking changes in RELEASES.md

Co-authored-by: Josh Gross <joshmgross@github.com>

__tests__/cacheUtils.test.ts

@@ -24,3 +24,11 @@ test('unlinkFile unlinks file', async () => {
 
   await fs.rmdir(testDirectory)
 })
+
+test('assertDefined throws if undefined', () => {
+  expect(() => cacheUtils.assertDefined('test', undefined)).toThrowError()
+})
+
+test('assertDefined returns value', () => {
+  expect(cacheUtils.assertDefined('test', 5)).toBe(5)
+})