Rename the remaining mentions of cratesfyi to docs-rs, docs_rs or similar.

[eddyb]

[Nemo157]

Also, there's an inconsistency between some environment variables being DOCS_RS_* and others being DOCSRS_*, would be good to standardize these.

[alb]

Which one should be used? Is it DOCS_RS_* or DOCSRS_*?

[jyn514]

I don't have a strong preference. I think more uses DOCS_RS currently so let's go with that.

[Nemo157]

I think it's actually the opposite

> rg --hidden '(DOCSRS|DOCS_RS)_[A-Z_]+' --only-matching --no-heading --no-filename --no-line-number | LC_ALL=C sort -u
DOCSRS_BUILD_ATTEMPTS
DOCSRS_MAX_FILE_SIZE
DOCSRS_MAX_FILE_SIZE_HTML
DOCSRS_MAX_POOL_SIZE
DOCSRS_MIN_POOL_IDLE
DOCS_RS_BUILD_CPU_LIMIT
DOCS_RS_DOCKER
DOCS_RS_LOCAL_DOCKER_IMAGE