making ordering explicit, and disabling blank issue submission to force
triage label to be set.

Issue template for the "blank issue" option

Issue template configuration is the only github configuration file I've found which does not support both `*.yaml` and `*.yml` extensions. Drat.

Provide a link to feedback.secondlife.com from the issue creation page.

We're currently building every single commit pushed to Github. This is
racking up $20k in build charges a month and is generally superfluous.

This changeset alters build triggers so that builds automatically run if
they are committed to a **shared branch**:

- `release/*` - A release stabilization branch
- `project/*` - A project viewer branch
- `main/*` - The default/stable branch

PR commits are also automatically built.

...need to build another commit? Developers can trigger one using a
manual workflow run.

in viewer's autobuild-package.xml.

Ensure that AUTOBUILD_VCS_BRANCH is set before the build.

Switch the build workflow from targeting the `main` branch of
viewer-build-util (which may receive breaking changes) to the stable
`v1` major version tag.

Only download and publish installers on public releases. This simplifies
the release process, as the flatten_files utility from
viewer-build-utils is not necessary this way. More importantly, it
doesn't clutter public releases with files that shouldn't be published
such as debug symbols.

for Mac and Windows. That's now done by subsequent jobs in the GitHub build.
Remove workflow step to upload installers before signing and packaging jobs.

Remove from viewer_manifest.py conditionals for 32-bit Windows or Mac.

Also bump to actions/checkout@v4, per dependabot.

"ASC Provider" was a credential accepted by altool, but switching from altool
to notarytool requires a Team ID instead.

Expect to find TEAM_ID in our repository secret NOTARIZE_CREDS_MACOS. Extract
it and pass it to sign-pkg-mac.

Add a Mac signing step to unpack the credentials bundled into
NOTARIZE_CREDS_MACOS so viewer-build-util/sign-pkg-mac need not know about
that peculiarity of our secrets formatting.

The viewer_manifest.py logic to determine the name of the viewer installer
.dmg is a little convoluted. Make it tell viewer-build-util/sign-pkg-mac that
name, rather than passing it all the relevant inputs and composing it
redundantly.

sign-pkg-mac also wants the viewer channel to determine the application name.

and uses new viewer-build-util/release-artifacts action.

instead of trying to checkout viewer-build-util (which doesn't work) and then
reference action subdirs from the filesystem.

Also engage (initial placeholder) actions to sign and package the
platform-specific application artifacts.

instead of having it implied by specifying the containing directory.

instead of distinct viewer-post-bugsplat-{windows,mac} repos.

In a Windows build tree, we don't actually have an app-named top directory, so
don't package its containing directory -- just the app dir itself, e.g.
"newview/Release".

In a Mac build tree, though we do have "Second Life Mumble.app", its parent
directory also contains other large stuff. Try posting a temp directory
containing a symlink to the .app.

Ditch the "!*.bat" exclusion: the presence of a second path (even an
exclusion) changes how upload-artifact nests its contents.

This unblocks ReleaseOS builds, and also preps for SL-19242.

Streamline build.sh's Uploads section.