refactor(devtools): set key in manifest.chrome.json (#55639)

This key comes from the release build of the Chrome extension. Setting it here configures the extension ID of a local build to match the extension ID of the public release. This makes Chrome recognize that local builds are the same extension leading to more intuitive behavior. It's also useful for allowlists of extension IDs to keep the local ID consistent.

PR Close #55639

devtools/projects/shell-browser/src/manifest/manifest.chrome.json

@@ -9,6 +9,7 @@
   "content_security_policy": {
     "extension_pages": "script-src 'self'; object-src 'self'"
   },
+  "key": "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAlm3JzpfmggVNDXe1uSVKq1btwWec4pOYefbB36CYj41bqUyw3xQqiAOCIlSAhl5GkQA/9PTixCNd14ix6RbI2yV8OeNt6oc0ca5BmEdGVj27lu32CgH5KbOc+AhyOAikoMq4IlgaWvqglZiyzd9KnL1wO/DqLDsZS0PV9oRwZk/8Eno2giZ1El4YQ5cNZ125JJR5z9KYAvxUs6bnDXAM71gW5sJwoUdgXQZhEIT18uSz0p2RiC0Ajjh4kx9c5Ll9naByXd3g5hjS8Ro5WbENRhxZtx1eEcgwC79l0pbJjI71i0QjbfLZn6syfHGMWsLyMc/ucv6d86tCPO8J1mU8iQIDAQAB",
   "icons": {
     "16": "assets/icon16.png",
     "48": "assets/icon48.png",