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

[aranjans]

Fixes #6583

This PR includes the following changes:

• Currently the regenerate script installs protoc-gen-go and protoc-gen-go-grpc in a workdir, but uses the system installed protoc which means that running the regenerate.sh script could result in all generated files being changed with a diff in protoc version for the generated files.
• Now we have a install_protoc.sh script(responsible for installing protobuf on client side in case its not present) which is called by vet.sh and regenerate.sh.

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 92 commits behind head on master.

❗ Current head b3106cc differs from pull request most recent head cee9875

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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]

This is how links to files in our repo @ master would look like https://github.com/grpc/grpc-go/blob/master/admin/admin.go

Also about this; why not just something like:

source ./scripts/install_protoc.sh

[arvindbr8]

nit: This still looks like a link to what to do. But just points to a script without the how to. Have you looked at my other comment that talked about why it might be nice to run install_protoc.sh also in this case?

[aranjans]

added few lines on how to use install_protoc.sh in case of manual run.

[arvindbr8]

LGTM, modulo two nits

[arvindbr8]

nit: remove this echo as well. The user doesnt have to know that the state changed and was reverted.

[aranjans]

Updated

[purnesh42H]

lgtm. Please update the PR description as discussed

[easwars]

The last /bin is not required here. @arvindbr8 and myself tested this. If the script is run as is currently written, it ends up putting the protoc binary in GOPATH/bin/bin.

Also, the script now ends up copying a readme.txt to the INSTALL_DIR. Can we not do that. Thanks.

[aranjans]

@easwars i have removed the extra /bin. For the second part, readme.txt is part of the zip of binary, so for now i am just doing rm "${INSTALL_DIR}/readme.txt".