refactor: replace {crul} with {httr2}

[maelle]

Fix #156

[maelle]

also need to use https://httr2.r-lib.org/reference/req_throttle.html

[dpprdan]

Yeah, watch out for https://github.com/ropensci/opencage/blob/main/R/zzz.R and https://github.com/ropensci/opencage/blob/9b57eefa9725822d00e1e48417f5948eeeb15db1/R/oc_config.R#L122-L126

Though I am sure you've seen that.

[maelle]

Oh: https://httr2.r-lib.org/reference/req_cache.html (not sure how to clear that cache)