[knitr] Update pdf cropping detection to latest knitr version and allow opt out using crop: false chunk option

[cderv]

This PR

• fix Correctly check ghostscript for cropping on Windows as per knitr 1.43 #5734
• fix Figures are always cropped in PDF output #5981

It update our R code to use the latest fix from yihui/knitr#2246 (when recent version of knitr is used)

and it adds support to use crop: false chunk option to opt out cropping feature in PDF.

Either at chunk level

```{r}
#| crop: false
library(ggplot2)
ggplot() + theme(plot.margin = margin(t=2,b=2,unit='cm')) # wide margins to see the effect (or lack thereof)
```

or globally

knitr:
  opts_chunk: 
    crop: false

The usual knitr way is crop: null but this is less known and easy to remember

knitr:
  opts_chunk: 
    crop: null

and

```{r}
#| crop: null
library(ggplot2)
ggplot() + theme(plot.margin = margin(t=2,b=2,unit='cm')) # wide margins to see the effect (or lack thereof)
```