[GSoC 2023] Modifying drivingdistance

[aryan1010]

This PR modifies one existing function:

• `pgr_drivingdistance:
  • Adding one new result column 'depth'.
  • Normalizing the output(Adding start_vid column for single vertex).

This is a final merge PR containing commits from several different PRs combined.

The intermediate PRs made on the GSoC-pgRouting repository are as follows:

Description	Pull Requests
pgr_drivingdistance	pgRouting/GSoC-pgRouting#293 pgRouting/GSoC-pgRouting#296 pgRouting/GSoC-pgRouting#305 pgRouting/GSoC-pgRouting#310 pgRouting/GSoC-pgRouting#311 pgRouting/GSoC-pgRouting#315 pgRouting/GSoC-pgRouting#321 pgRouting/GSoC-pgRouting#329 pgRouting/GSoC-pgRouting#331 pgRouting/GSoC-pgRouting#334 pgRouting/GSoC-pgRouting#338 pgRouting/GSoC-pgRouting#344

The wiki page with more details on this project can be found here.

[krashish8]

Please also update the NEWS and release_notes.rst file, similar to the other GSoC PRs.

[aryan1010]

@robe2 @krashish8 i have updated news and release_notes

[krashish8]

You don't have to update NEWS manually. Use this script to generate NEWS: tools/release-scripts/notes2news.pl

Also, the release_notes.rst file is not formatted correctly. The links are written in a different way in an rst file (you can refer how other students did). NEWS will resemble markdown format.

[robe2]

Links are written in a different format in rst file: https://sublime-and-sphinx-guide.readthedocs.io/en/latest/references.html#links-to-external-web-pages

I think @Aniket-debug also needs to fix this in the release notes. Otherwise, this looks good. 🎉

I think @squarege made this mistake too. I'll go ahead and merge this for expediency.