Add workflow_dispatch trigger to GHA workflows (GH-27873)

.github/workflows/build.yml

@@ -4,6 +4,7 @@ name: Tests
 # it prevents to mark a job as mandatory. A PR cannot be merged if a job is
 # mandatory but not scheduled because of "paths-ignore".
 on:
+  workflow_dispatch:
   push:
     branches:
     - 'main'

.github/workflows/build_msi.yml

@@ -1,6 +1,7 @@
 name: TestsMSI
 
 on:
+  workflow_dispatch:
   push:
     branches:
     - 'main'

.github/workflows/doc.yml

@@ -1,6 +1,7 @@
 name: Docs
 
 on:
+  workflow_dispatch:
   #push:
   #  branches:
   #  - 'main'