devcontainer: Use our own dockerfile (#42166)

Switch to using our own dockerfile, and install the required
dependencies into our image.
In follow-ups we can build the docker image in CI, so that users can
download a prebuilt docker image to save time.

Testing: Manually tested by opening servo in the devcontainer and
running `./mach build`

Signed-off-by: Jonathan Schwender <schwenderjonathan@gmail.com>

.devcontainer/devcontainer.json

@@ -2,33 +2,17 @@
 // README at: https://github.com/devcontainers/templates/tree/main/src/ubuntu
 {
 	"name": "Ubuntu",
-	"image": "mcr.microsoft.com/devcontainers/base:noble",
-	"features": {
-		"ghcr.io/devcontainers/features/rust:1": {
-			"version": "1.91.0",
-			"profile": "default",
-			"components": "clippy,llvm-tools,rustc-dev,rust-analyzer,rust-src,rustfmt"
-		},
-		"ghcr.io/devcontainers-extra/features/uv:1": {
-			"version": "latest"
-		}
+	"build": {
+		"dockerfile": "Dockerfile",
+		"context": ".."
 	},
-	// Uncomment the following when using podman (rootless)
-	// Update the uid and gid, to your local users uid and gid (run `echo $UID` and `echo $GID`)
-	// "runArgs": ["--userns=keep-id:uid=1000,gid=1000"],
-	// "containerUser": "vscode",
-	
-	// Uncomment the following when using rootless docker 
-	// "containerUser": "root",
-	// "remoteUser": "root",
-	// "updateRemoteUserUID": false,
 
 
-	// Use 'postCreateCommand' to run commands after the container is created.
-	// This takes more time on the first run compared to pulling a prebuilt image layer,
-	// but makes sure the bootstrapped dependencies are always up to date.
+	// Most dependencies are installed in the image, but we run mach bootstrap to ensure
+	// the environment matches what's expected in the current servo version, which might 
+	// have changed since the image was built.
 	"postCreateCommand":
-		"./mach bootstrap --force",
+		"./mach bootstrap --yes",
 
 	"containerEnv": {
 		"CC": "clang",