tests/server: sync wait_ms() with the libcurl implementation

[vszakats]

It contains a series of bugfixes and updates applied to libcurl's
Curl_wait_ms() over the years, but missed from the copy in
tests/server/util.c:

• d65321f,
  52e8221,
  5912da2
• 4a8f459
• 1ad49fe
• 4a8f459
• 1ad49fe

It fixes wait_ms() to check for, and return SOCKERRNO. Fixing error
handling on Windows.

Also:

• tests/server: change callers to check SOCKERRNO.
• wait_ms(): fix to check for the correct error code on Windows.
  Pending for Curl_wait_ms(): core: stop redefining E* macros on Windows, map EACCES, related fixes #16621.
• Curl_wait_ms(): tidy-up Sleep() argument cast (nit).
• lib/curl_trc: drop an unused header.

[bagder]

You can simplify this a lot more by just not caring about why wait_ms() fails if it does...

[vszakats]

Ah, just merged. I guess we could simplify, but my next step would be to drop this dupe a re-use Curl_wait_ms(). Then continue with cleanups there. The fail reason also seems unimportant there, though for select.c code it may be used upper in the call chain.