CI: fetch Proxifier and Spyware Doctor AV LSP's from a source we control

Closes #1938

Author: belm0

.github/workflows/ci.yml

@@ -27,13 +27,13 @@ jobs:
             extra_name: ', with Komodia LSP'
           - python: '3.8'
             arch: 'x64'
-            lsp: 'https://www.proxifier.com/download/legacy/ProxifierSetup342.exe'
-            lsp_extract_file: ''
+            lsp: 'https://raw.githubusercontent.com/python-trio/trio-ci-assets/master/ProxifierSetup.zip'
+            lsp_extract_file: 'ProxifierSetup.exe'
             extra_name: ', with IFS LSP'
           - python: '3.8'
             arch: 'x64'
-            lsp: 'http://download.pctools.com/mirror/updates/9.0.0.2308-SDavfree-lite_en.exe'
-            lsp_extract_file: ''
+            lsp: 'https://raw.githubusercontent.com/python-trio/trio-ci-assets/master/sdasetup-9.0.0.912_Trial.zip'
+            lsp_extract_file: 'sdasetup-9.0.0.912_Trial.exe'
             extra_name: ', with non-IFS LSP'
     steps:
       - name: Checkout