Stop shipping codex-exec-server in release artifacts (#57628)

## What changed

- Remove the standalone executor from CLI and app-server packages, release binary lists, and Bazel runtime archives.
- Remove the package builder's `--exec-server-bin` option and `execServer` metadata, along with executor-specific installer checks, signing configuration, and package smoke tests.
- Keep the standalone executor available to build from source.

GitOrigin-RevId: ada4c92c092e3c7a3067129913e99f4606f7adc8

codex-rs/exec-server-cli/BUILD.bazel

@@ -1,6 +1,4 @@
 load("//:defs.bzl", "codex_rust_crate")
-load("//bazel/platforms:release_binaries.bzl", "multiplatform_binaries")
-load("//bazel/rules:runtime_package.bzl", "release_binary")
 
 codex_rust_crate(
     name = "exec-server-cli",
@@ -11,7 +9,3 @@ codex_rust_crate(
     # The standalone integration test launches native OS sandboxes itself.
     test_tags = ["no-sandbox"],
 )
-
-release_binary(binary = ":codex-exec-server")
-
-multiplatform_binaries(name = "codex-exec-server")