refactor(Containerfile): use multi stage logic

[axel7083]

Description

The current Containerfile is not building the dist themself, it copies from outside the containers.

extension-postgresql/Containerfile

Lines 1 to 8 in 16cb3ce

	FROM scratch as builder
	COPY packages/backend/dist/ /extension/dist
	COPY packages/backend/package.json /extension/
	COPY packages/backend/pg-icon.woff2 /extension/
	COPY packages/backend/media/ /extension/media
	COPY LICENSE /extension/
	COPY packages/backend/icon.png /extension/
	COPY README.md /extension/

To be able to unify and share GitHub actions we need to make Containerfile of extensions behaving the same. Example of Containerfile to reuse available in podman-desktop/gh-extensions-actions#5