[msexchange] Automate latest releases retrieval

[marcwrobel]

Based on https://learn.microsoft.com/exchange/new-features/build-numbers-and-release-dates.

Microsoft is maintaining multiple CU builds for a given release cycle at the same time: maybe this must be reflected on https://endoflife.date/msexchange first.

[stbuehler]

The list of the currently supported CUs can be found here: https://learn.microsoft.com/en-us/exchange/plan-and-deploy/supportability-matrix?view=exchserver-2019#supported-versions-and-builds

I don't think any of the sites show end-of-life dates though, only what is available / currently supported.

In case someone needs inspiration on how to build real complicated parsers for those sites, see my icinga check script in https://github.com/stbuehler/exchange-version-check