scripts: improve regenerate.sh to use the correct proto compiler version

[aranjans]

Fixes #6583

RELEASE NOTES: n/a

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.70%. Comparing base (adf976b) to head (b3106cc).
Report is 46 commits behind head on master.

❗ Current head b3106cc differs from pull request most recent head 5878795. Consider uploading reports for the commit 5878795 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7064      +/-   ##
==========================================
- Coverage   81.24%   80.70%   -0.54%     
==========================================
  Files         345      346       +1     
  Lines       33941    33802     -139     
==========================================
- Hits        27574    27280     -294     
- Misses       5202     5355     +153     
- Partials     1165     1167       +2     

see 33 files with indirect coverage changes

[arvindbr8]

I would prefer if we didnt track the version of protoc in different places.

What might be nicer is if both regenerate.sh and vet.sh points to the same place to install protoc. Also note ./vet.sh -install basically does the same thing of installing protoc for Github Actions.

I prefer creating a new script which installs protoc based on the ${OS}. And for ./vet -install I could call into the script to install the linux and x86_64 flavor of protoc. And do something similar for regenerate.sh

[arvindbr8]

I've made a few comments on your change. Could you please take a look at it?

[arvindbr8]

A couple of comments from the previous pass still seems to be unaddressed:

1. https://github.com/grpc/grpc-go/pull/7064/files#r1569226189
2. https://github.com/grpc/grpc-go/pull/7064/files#r1569224986

I also have some more comments. I think it looks overall okay if the aim is to fix the current issue. But could you please open a new issue which talks about the TODOs from this PR?

[github-actions]

This PR is labeled as requiring an update from the reporter, and no update has been received after 6 days. If no update is provided in the next 7 days, this issue will be automatically closed.

[aranjans]

fyi: was caught up in other issues. I am working on this right now on priority, will update the PR soon.

[aranjans]

@arvindbr8 In contrast to this comment, first comment is resolved but i didn't understand the second one. Can you be more specific on that?