Add godoc linter

[dfawley]

Since removing golint, we've had numerous occasions of missing docstrings. This seems like the consensus replacement for golint: https://github.com/mgechev/revive -- we should set it up to at least check the docstrings.

EDIT:

• add the Revive inter in quite mode: tools: Add github.com/mgechev/revive #7472**

• Enforce Revive Linter: vet: enforce revive linter #7589

• fix below existing lint issues and enable the disabled rule

#7575 fixes

• 83 exported

#7574 fixes

• 8 package-comments

#7552 fixes

• 15 redefines-builtin-id

#7528 fixes

• 6 var-declaration
• 3 indent-error-flow
• 1 increment-decrement
• 1 superfluous-else

#7577 #7580 fixes

• 546 unused-parameter
• 28 var-naming (Ignore reflection/test/grpc_testing_not_regenerate/)
• 1 context-as-argument (Ignore reflection/test/grpc_testing_not_regenerate/)

[purnesh42H]

Before we enforce revive, we need to fix existing lint issues caught in #7472 as part of vet check.

Its fine to change several files in a single PR if they all fix one type of issue or are otherwise related. However, be reasonable and try to keep the PRs small enough to make it not take a long time to review and avoid merge conflicts.

[janardhanvissa]

@purnesh42H Please assign me this issue.

[janardhanvissa]

@purnesh42H Right now, In the tests (vet) I'm getting like don't use an underscore in package name https://revive.run/r#var-naming.
It's not expecting underscore but by default as it's generating from the proto file like ("google.golang.org/grpc/reflection/test/grpc_testing_not_regenerate"). So, what need to do for further. Please suggest.

[janardhanvissa]

@purnesh42H Fixed some of the godoc-linter issues. Please review and let me know if any changes are required. Please find the PR below.
#7501

[janardhanvissa]

@purnesh42H Fixed linter issues for superfluous-else, increment-decrement, indent-error-flow, var-declaration. Please review the changes.

janardhanvissa#1