Speed up POSIX calls in part 6 that were recently revised to facilitate backward compatibility with older R versions

[vincentvanhees]

Fixes #1263 by revising the previous edits that made the code backward compatible with R 4.2.0 but then slowed down part 6.

@forget999 would you mind testing that GGIR part 6 is of acceptable speed again in this update? (I am travelling and do not have time for elaborate testing in the upcoming 2 weeks).

You can do so by installing GGIR via:
remotes::install_github("wadpac/GGIR", ref = "issue1263_POSIXct_speed")

Checklist before merging:

• Existing tests still work (check by running the test suite, e.g. from RStudio).
• Added tests (if you added functionality) or fixed existing test (if you fixed a bug).
• Clean code has been attempted, e.g. intuitive object names and no code redundancy.
• Documentation updated:
  • Function documentation
  • Chapter vignettes for GitHub IO
  • Vignettes for CRAN
• Corresponding issue tagged in PR message. If no issue exist, please create an issue and tag it.
• Updated release notes in inst/NEWS.Rd with a user-readable summary. Please, include references to relevant issues or PR discussions.
• Added your name to the contributors lists in the DESCRIPTION file, if you think you made a significant contribution.
• GGIR parameters were added/removed. If yes, please also complete checklist below.

If NEW GGIR parameter(s) were added then these NEW parameter(s) are:

• documented in man/GGIR.Rd
• included with a default in R/load_params.R
• included with value class check in R/check_params.R
• included in table of vignettes/GGIRParameters.Rmd with references to the GGIR parts the parameter is used in.
• mentioned in NEWS.Rd as NEW parameter

If GGIR parameter(s) were deprecated these parameter(s) are:

• documented as deprecated in man/GGIR.Rd
• removed from R/load_params.R
• removed from R/check_params.R
• removed from table in vignettes/GGIRParameters.Rmd
• mentioned as deprecated parameter in NEWS.Rd
• added to the list in R/extract_params.R with deprecated parameters such that these do not produce warnings when found in old config.csv files.

[forget999]

Thanks for your work, I will test it in the next two days. I will give you timely feedback when the test is completed. Have a nice trip!

[forget999]

I have installed the new GGIR version and tested it. Unfortunately, the running time of part 6 is still very long, up to an hour. I am currently using R version 4.4.2, and the computer configuration is 32G RAM, which is enough to run GGIR. If you need any more test information, please let me know. I look forward to further fixes for this bug, thank you.