Update FAQs, HPC guide, and Gentle Introduction

[tomvothecoder]

Description

• Related to #589
• Merge to #489 before this PR because the Gentle Introduction guide includes Dask parallelism content, which we can link to the new Dask notebook in that PR
• Closes #651

Summary of Changes

introduction-to-xcdat.ipynb

• Updated overview section with conda env setup instructions similar to other notebooks
• Re-ran outputs with latest version of xcdat=0.7.0 and xarray=2024.03.0
• Replace add_bounds=True with add_bounds=["X", "Y", "T"]
• Replace broken dataset filepath to esgf.nci.org.au to esgf-data1.llnl.gov
• Add some descriptions to Dask parallelism section and run .compute()
• TODO: Add link to xCDAT parallelism notebook from PR #489

faqs.rst

• Remove mention of striving to support common non-CF compliant metadata since I don't think we're actually doing that. The only non-CF compliant metadata xCDAT supports right now is decoding "months since ..." and "years since ...".
• Add info about spatial averager supporting rectilinear grid
• Add info about xCDAT's fall-back mapping table for axes
• Update section on how bounds are generated with latest APIs
• Replace "Data Wrangling" header to "xCDAT Does Not Support Model-Specific Data Wrangling"

getting-started-hpc-jupyter.rst

• Add cartopy to conda command
• Remove mentions of xesmf being an optional dependency and remove xesmf from conda command

Checklist

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] My changes generate no new warnings
• [ ] Any dependent changes have been merged and published in downstream modules

If applicable:

• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass with my changes (locally and CI/CD build)
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)