Add more detail to greta_sitrep()

[njtierney]

Relevant issue #612

Goals:

• R & Rstudio version
• Greta version - and point to whether installed from CRAN/github etc.
• Paths to Python, TF, and TFP. This might help debug issues with this
• Paths to greta env (if used)
• Note if greta env is used
• Don't just print TF/TFP versions, list where they are installed
• List python version, and where it is installed, which environment is used
• Add various helper functions to identify where TF is installed
• Add various helper functions to identify where TFP is installed

[njtierney]

Currently can't seem to work out where TF and TFP are installed.

I'm also wondering if a verbose = TRUE option might be useful here? The info is getting a little bit long!

> greta_sitrep()

── R ─────────────────────────────────────
• version: 4.4.2
• path:
/Library/Frameworks/R.framework/Resources

── greta ─────────────────────────────────
• version: 0.4.5.9000
• path:
"/Users/nick/github/greta-dev/greta"

── python ────────────────────────────────
✔ python (v3.10) available    
• path:
"/Users/nick/github/greta-dev/greta"
• path:
"/Users/nick/Library/r-miniconda-arm64"

── TensorFlow ────────────────────────────
✔ TensorFlow (v2.15.0) available  
• R path:
/Users/nick/Library/R/arm64/4.4/library/tensorflow
• python path:
"/Users/nick/github/greta-dev/greta"

── TensorFlow Probability ────────────────
✔ TensorFlow Probability (v0.23.0) availa…
• R path:
/Users/nick/Library/R/arm64/4.4/library/tensorflow
• python path:
"/Users/nick/github/greta-dev/greta"

── greta conda environment ───────────────
✔ greta conda environment available       
• path:
/Users/nick/Library/r-miniconda-arm64/envs/greta-env-tf2/bin/python

── greta usability ───────────────────────
ℹ greta is ready to use!

Compared to:

> greta_sitrep()
✔ python (v3.10) available    
✔ TensorFlow (v2.15.0) available  
✔ TensorFlow Probability (v0.23.0) availa…
✔ greta conda environment available       
ℹ greta is ready to use!

So perhaps some option like:

greta_sitrep(verbosity = "verbose")

By default, and then some note that appears at the end of the messages that tells you about the verbose option?

Other options could be "quiet", "minimal", "verbose" ?