GHA: make element-web and cypress workflows reusable (#10969)

* GHA: make `element-web` workflow reusable

... so that we can call it from the js-sdk repo

* GHA: make `cypress.yaml` a reusable workflow

... so that we can call it from js-sdk

* GHA: give cypress.yaml a `rust-crypto` parameter

* Update .github/workflows/cypress.yaml

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

* remove workflow_dispatch

---------

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

.github/workflows/element-web.yaml

@@ -12,6 +12,20 @@ on:
         branches: [develop, master]
     repository_dispatch:
         types: [upstream-sdk-notify]
+
+    # support triggering from other workflows
+    workflow_call:
+        inputs:
+            react-sdk-repository:
+                type: string
+                required: true
+                description: "The name of the github repository to check out and build."
+
+            matrix-js-sdk-sha:
+                type: string
+                required: false
+                description: "The Git SHA of matrix-js-sdk to build against. By default, will use a matching branch name if it exists, or develop."
+
 concurrency:
     group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
     cancel-in-progress: true
@@ -25,7 +39,10 @@ jobs:
         name: "Build Element-Web"
         runs-on: ubuntu-latest
         steps:
-            - uses: actions/checkout@v3
+            - name: Checkout code
+              uses: actions/checkout@v3
+              with:
+                  repository: ${{ inputs.react-sdk-repository || github.repository }}
 
             - uses: actions/setup-node@v3
               with:
@@ -33,6 +50,9 @@ jobs:
 
             - name: Fetch layered build
               id: layered_build
+              env:
+                  # tell layered.sh to check out the right sha of the JS-SDK, if we were given one
+                  JS_SDK_GITHUB_BASE_REF: ${{ inputs.matrix-js-sdk-sha }}
               run: |
                   scripts/ci/layered.sh
                   JSSDK_SHA=$(git -C matrix-js-sdk rev-parse --short=12 HEAD)
@@ -44,7 +64,6 @@ jobs:
               run: cp element.io/develop/config.json config.json
               working-directory: ./element-web
 
-            # After building we write the version file and the react-sdk sha so our cypress tests are from the same sha
             - name: Build
               env:
                   CI_PACKAGE: true
@@ -52,9 +71,13 @@ jobs:
               run: |
                   yarn build
                   echo $VERSION > webapp/version
-                  echo $GITHUB_SHA > webapp/sha
               working-directory: ./element-web
 
+            # Record the react-sdk sha so our cypress tests are from the same sha
+            - name: Record react-sdk SHA
+              run: |
+                  git rev-parse HEAD > element-web/webapp/sha
+
             - name: Upload Artifact
               uses: actions/upload-artifact@v3
               with: