fix: Test flake when installing yarn dependencies on MacOS (#436)

This fixes #433 - a test flake in E2E (intermittent `ESOCKETTIMEDOUT` errors on MacOS).

The main issue is that, occasionally, for very large dependencies (like `@material-ui/icons`) - yarn can actually time out! We researched this in-depth in v1: https://github.com/coder/m/pull/10040 and fixed it successfully there, by increasing the timeout for yarn.

However, this also highlighted the fact that our `node_modules` caching behavior wasn't correct - we should very rarely see a timeout issue like this, because `@material-ui/icons` should be cached.

It turns out that we weren't falling back to the latest cached `node_modules` if there was a miss - so anytime the lock file changed, we'd  invalidate the cache, and not restore the previous one. This can be improved by using the [`restore-keys`](https://github.com/coder/m/pull/10040) parameter of the [`@actions/cache`](https://github.com/actions/cache)... and in fact we already do this for the `go` dependencies.

So this fix does two things:
- Improve the caching behavior, such that we should rarely have to install `@material-ui/icons` (and other large dependencies) 
- When we do have to install, update the timeout so that we can avoid random `ESOCKETTIMEDOUT` errors

.github/workflows/coder.yaml

@@ -61,6 +61,8 @@ jobs:
             **/node_modules
             .eslintcache
           key: js-${{ runner.os }}-test-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            js-${{ runner.os }}-
 
       - name: Install node_modules
         run: ./scripts/yarn_install.sh
@@ -108,6 +110,8 @@ jobs:
             **/node_modules
             .eslintcache
           key: js-${{ runner.os }}-test-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            js-${{ runner.os }}-
 
       - name: Install node_modules
         run: ./scripts/yarn_install.sh
@@ -250,6 +254,8 @@ jobs:
             **/node_modules
             .eslintcache
           key: js-${{ runner.os }}-test-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            js-${{ runner.os }}-
 
       # Go is required for uploading the test results to datadog
       - uses: actions/setup-go@v2
@@ -312,6 +318,8 @@ jobs:
             **/node_modules
             .eslintcache
           key: js-${{ runner.os }}-test-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: |
+            js-${{ runner.os }}-
 
       # Go is required for uploading the test results to datadog
       - uses: actions/setup-go@v2

site/.yarnrc

@@ -0,0 +1 @@
+network-timeout 300000