[changelog tool] missing logs from the latest beta tag

now our beta packages will be released with `beta` tag not `next` tag.
So if the newest package is the `beta` tag. changelog tool can't use `beta` tag logs as the `originalChangeLogContent `

currently in changelog tool, it only compares the latest tag and next tag. We need support the beta tag.

see
https://github.com/Azure/azure-sdk-tools/blob/main/tools/js-sdk-release-tools/src/common/changelog/automaticGenerateChangeLogAndBumpVersion.ts#L117-L128

Start at tools/js-sdk-release-tools/src/common/changelog/automaticGenerateChangeLogAndBumpVersion.ts, especially lines 117-128. Trace how the changelog tool selects the latest and next tags, then extend the behavior to use beta-tag logs when beta is the newest package tag. Done means beta releases no longer omit their changelog content.

Written by the indexing model from the issue text.