delegate build to buildx bake

[ndeloof]

What I did

introduce support for COMPOSE_BAKE to opt-in for build to be delegated to buildx bake. Compose generates a bake json config from application model and executes bake, which (we assume) better knows how to orchestrate build steps for best efficiency.

Related issue

(not mandatory) A picture of a cute animal, if possible in relation to what you did

[thaJeztah]

Perhaps could also be worth (if compose reads the cli config) to consider either an option in features, or plugins (plugins allows plugin-specific options to be set), which would allow opt-in/opt-out of this without having to use an env-var;
https://github.com/docker/cli/blob/9861ce90fd6b8ddca19db5f803dcbef9a583e9e1/cli/config/configfile/file.go#L42-L44

	Plugins              map[string]map[string]string `json:"plugins,omitempty"`
	Aliases              map[string]string            `json:"aliases,omitempty"`
	Features             map[string]string            `json:"features,omitempty"`

(in addition to an env-var probably)

[ndeloof]

we never used this mechanism in the past for optional/experimental docker compose features

[thaJeztah]

Yeah, my thinking here was that the cli-config would more easily allow this to be set as a default, which could also allow (e.g.) it to be set through docker desktop "settings".