Support specifying language for `infra/helper.py pull_images`

Hello,

multiple guides currently suggest using `infra/helper.py pull_images`, most notably "[Reproducing OSS-Fuzz issues](https://google.github.io/oss-fuzz/advanced-topics/reproducing/#pull-the-latest-docker-images)". That command seems to pull the images for all languages (Swift, Go, Rust, ...).
However, I assume that for a single target project only one of these language specific images would be needed.

Would it be possible to extend `pull_images` to support specifying the language, and to update the guides to recommend specifying a language to avoid pulling redundant multiple large Docker images?
(Or if `build_image` and `build_fuzzers` normally suffice, maybe not recommend `pull_images`?)