Update protobuf/protoc version installed in CI.

[Yury-Fridlyand]

Issue #, if available:

N/A

Description of changes:

1. Update protobuf/protoc version installed in CI.
2. Minor reorganize CI to reuse install-shared-dependencies action.

Reason:
apt-get installs protoc v. 3.12, brew (on mac) installs 3.24 (24.3), whereas 3.25 (25.1) is already available. Having different versions on different platform may lead to issues.
For example, in java, 3.25 generates following functions:

response.hasRequestError()
response.hasClosingError()
response.hasConstantResponse()

and so on.
protoc v.3.12 doesn't generate these functions, but they are essential to validate the response content.

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