Add hash for OR-Tools, remove unneccessary pip repositories call

[jamesreprise]

What is the goal of this PR?

Currently, there are a number of warnings output by Bazel upon syncing dependencies. These four warnings provide some recommendations as to how we can improve the state of the repository. Additionally, fixing the problems associated with warnings is good practice as it prevents developers from becoming used to warnings and potentially missing something important. Case in point: if someone were to compromise the google/or-tools repository and replace the releases we download with compromised packages, Bazel wouldn't know.

We are currently missing a hash for our http_archive downloads for google_or_tools_*. This reduces hermeticity.

We currently call pip_repositories, despite the fact that it is a deprecated method. See the method body:

def pip_repositories():
    """
    Obsolete macro to pull in dependencies needed to use the pip_import rule.

    Deprecated:
        the pip_repositories rule is obsolete. It is not used by pip_install.
    """

    # buildifier: disable=print
    print("DEPRECATED: the pip_repositories rule has been replaced with pip_install, please see rules_python 0.1 release notes")

What are the changes implemented in this PR?

• We have added a sha256 argument to all of our google_or_tools_* http_archive calls, increasing hermeticity.
• We have removed our call to pip_repositories.

[grabl]

PR Review Checklist

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Code

• Packages, classes, and methods have a single domain of responsibility.
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• The architecture intuitively reflects the application domain, and is easy to understand.
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• The architecture is extensible and scalable.

[jamesreprise]

Working with typedb and typedb-studio.

https://grabl.io/jamesreprise/typedb/0e51786f44fbe089bc17e4ab3d355610574d08cb
https://grabl.io/jamesreprise/typedb-studio/1068a67ca017f2635365b50f1b8991fa0ba348fc