Remove unbuildable exchdapi

[Avasam]

From what I can tell, these API are no longer provided in any obtainable SDK. The exchdapi module also hasn't been built for 64 bits since 2010 (pywin32 v218.5 in 4cdae6c) and at all since 2016 (pywin32 v220 in e94ce71)

---

Research notes:

None of the missing functions, including those missing in 64 bit, can be found anywhere in any documentation (except stuff referencing pywin32, and https://github.com/bicomsystems/outcall2/blob/master/outlook/exchange/ which is a project for VS2010, but also commented some of them out for similar reasons)

The minimum Visual C++ supported by Python is now 14.x (ie: VS2015): https://wiki.python.org/moin/WindowsCompilers#Which_Microsoft_Visual_C.2B-.2B-_compiler_to_use_with_a_specific_Python_version_.3F

Also of note: Exchange servers 2010 and 2013 are completely impossible to download:
https://learn.microsoft.com/en-us/exchange/updates-for-exchange-2013-exchange-2013-help (linked blog posts still work, but they contain dead download links) & https://learn.microsoft.com/en-us/previous-versions/office/exchange-server-2010/bb124265(v=exchg.141)

Exchange servers 2016 & 2019 have a planned EOL for October 14th 2025 and a migration path to "Exchange Server Subscription Edition":
https://learn.microsoft.com/en-us/lifecycle/products/exchange-server-2016 & https://learn.microsoft.com/en-us/lifecycle/products/exchange-server-2019

I was gonna try and see if I could install a more recent version to find if it offered any of the missing features, but it looks like there's quite a bit of prerequisite to install them: https://learn.microsoft.com/en-us/exchange/new-features/updates?view=exchserver-2016

The (very old) 2003 server has an SDK, but it references a name (ExchTools.exe) and install path, but no download link: https://learn.microsoft.com/en-us/previous-versions/office/developer/exchange-server-2003/ms987923(v=exchg.65)

The only downloadable SDK I could find is from 2007 and requires an active subscription: https://my.visualstudio.com/Downloads?q=exchange%20sdk (check the box "All downloads")

#1018 (comment)

There is no 64bit lib. Also, there is an old recommendation from support against using it: EDK Library == Badness