Optimize container images for startup (#6547)

* Optimize container images for startup

This change adjusts how to handle runner payloads to support
container builds where we keep them extracted in the filesystem.
This makes it easier to optimize the cpu/cuda vs cpu/rocm images for
size, and should result in faster startup times for container images.

* Refactor payload logic and add buildx support for faster builds

* Move payloads around

* Review comments

* Converge to buildx based helper scripts

* Use docker buildx action for release

build/darwin/amd64/placeholder

@@ -0,0 +1 @@
+This is here to make sure the build/ directory exists for the go:embed command

build/darwin/arm64/placeholder

@@ -0,0 +1 @@
+This is here to make sure the build/ directory exists for the go:embed command

build/embed_darwin_amd64.go

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+package build
+
+import "embed"
+
+// Darwin payloads separated by architecture to avoid duplicate payloads when cross compiling
+
+//go:embed darwin/amd64/*
+var EmbedFS embed.FS

build/embed_darwin_arm64.go

@@ -0,0 +1,8 @@
+package build
+
+import "embed"
+
+// Darwin payloads separated by architecture to avoid duplicate payloads when cross compiling
+
+//go:embed darwin/arm64/*
+var EmbedFS embed.FS

build/embed_linux.go

@@ -0,0 +1,6 @@
+package build
+
+import "embed"
+
+//go:embed linux/*
+var EmbedFS embed.FS

build/embed_unused.go

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+//go:build !linux && !darwin
+
+package build
+
+import "embed"
+
+// unused on windows
+var EmbedFS embed.FS

build/linux/amd64/placeholder

@@ -0,0 +1 @@
+This is here to make sure the build/ directory exists for the go:embed command

build/linux/arm64/placeholder

@@ -0,0 +1 @@
+This is here to make sure the build/ directory exists for the go:embed command