Check performance of wrapper functions

[nuest]

Reported via email:

niwaClimate <- SOS(url = "https://climate-sos.niwa.co.nz",
binding = "KVP",
useDCPs = FALSE,
version = "2.0.0")

Each function call can take 5-10 seconds to retrieve some basic sites and phenomena information, which seems a bit long.

For example,

sites <- sites(sos = niwaClimate, empty = TRUE)
siteList <- siteList(sos = niwaClimate)
phenomena <- phenomena(sos = niwaClimate,
includeTemporalBBox = TRUE,
includeSiteId = TRUE)

Some profile analysis may point towards potential code optimisation places.

For example, for the phenomena function, a profile indicates that the
function parseTimePosition takes up a good chunk of the processing time.

@EHJ-52n @BenGraeler Would be great if you can support here.