Permit users to choose latest preview version or latest stable version in pypi to compare

[msyyc]

Now Mgmt SDK follow the following rule to generate changelog:

• If we are going to release preview package, we will compare with latest public package no matter it is preview or stable to generate changelog
• If we are going to release stable package, we will compare with latest public stable package to generate SDK

So we hope breaking change detector could add config like --latest-stable,

• when true, compare with latest stable version in pypi
• when false, compared with latest version in pypi, no matter it is stable or preview.

For example, if a package named "azure-mgmt-test" has already 1.0.0b1, 1.0.0, 1.1.0b1 in pypi,

• if is going to release new preview version, there is need to compare with 1.1.0b1
• if is gong to release new stale version, there is need to compare with 1.00

[raych1]

@catalinaperalta
please prioritize this issue as it is blocking the integration with the spec PR pipeline.

[catalinaperalta]

looking into this

[catalinaperalta]

FYI I have a PR addressing this issue. Adding a --latest-pypi-version flag to the tool that you'll be able to pass for the mgmt plane cases where you need to compare against the last published preview. Since data-plane will also be using the tool, I'm leaving comparing breaking changes with the last published stable version as the default scenario.