CI: Use npm ci rather than npm install

`npm ci` doesn't try to reconcile package.json with package-lock.json,
nor with any existing packages in `node_modules`. `npm ci` simply
deletes `node_modules` and uses the packages from `package-lock.json`.

As a result, `npm ci` is much, much faster than `npm install`.
We should use it wherever possible.

Author: DeeDeeG

script/vsts/nightly-release.yml

@@ -4,11 +4,11 @@ jobs:
       vmImage: 'ubuntu-latest'
     steps:
       # This has to be done separately because VSTS inexplicably
-      # exits the script block after `npm install` completes.
+      # exits the script block after `npm ci` completes.
       - script: |
           cd script/vsts
-          npm install
-        displayName: npm install
+          npm ci
+        displayName: npm ci
       - script: node script/vsts/get-release-version.js --nightly
         name: Version
         env:
@@ -38,11 +38,11 @@ jobs:
       - template: platforms/templates/preparation.yml
 
        #This has to be done separately because VSTS inexplicably
-       #exits the script block after `npm install` completes.
+       #exits the script block after `npm ci` completes.
       - script: |
           cd script/vsts
-          npm install
-        displayName: npm install
+          npm ci
+        displayName: npm ci
 
       - task: DownloadBuildArtifacts@0
         inputs:
@@ -77,8 +77,8 @@ jobs:
 
       - script: |
           cd script/lib
-          npm install
-        displayName: npm install
+          npm ci
+        displayName: npm ci
       - script: |
           cd script/lib/update-dependency
           node index.js

script/vsts/pull-requests.yml

@@ -6,11 +6,11 @@ jobs:
       vmImage: 'ubuntu-latest'
     steps:
       # This has to be done separately because VSTS inexplicably
-      # exits the script block after `npm install` completes.
+      # exits the script block after `npm ci` completes.
       - script: |
           cd script/vsts
-          npm install
-        displayName: npm install
+          npm ci
+        displayName: npm ci
       - script: node script/vsts/get-release-version.js
         name: Version
         env:

script/vsts/release-branch-build.yml

@@ -10,11 +10,11 @@ jobs:
       vmImage: 'ubuntu-latest'
     steps:
       # This has to be done separately because VSTS inexplicably
-      # exits the script block after `npm install` completes.
+      # exits the script block after `npm ci` completes.
       - script: |
           cd script/vsts
-          npm install
-        displayName: npm install
+          npm ci
+        displayName: npm ci
       - script: node script/vsts/get-release-version.js
         name: Version
         env:
@@ -43,13 +43,13 @@ jobs:
 
     steps:
       # This has to be done separately because VSTS inexplicably
-      # exits the script block after `npm install` completes.
+      # exits the script block after `npm ci` completes.
       - script: |
           cd script/vsts
-          npm install
+          npm ci
         env:
           GITHUB_TOKEN: $(GITHUB_TOKEN)
-        displayName: npm install
+        displayName: npm ci
 
       - task: DownloadBuildArtifacts@0
         inputs: