CI: move Azure jobs to GHA, fix fallouts, sshserver, runtests tweaks

CI:

- GHA/windows: enable OpenSSH server, SysInternals `handle`, `impacket`.
Skip `impacket` on MSYS2 due

CI: move Azure jobs to GHA, fix fallouts, sshserver, runtests tweaks

CI:

- GHA/windows: enable OpenSSH server, SysInternals `handle`, `impacket`.
Skip `impacket` on MSYS2 due to install failure.
Skip OpenSSH server for old/standalone mingw-w64 (building curl
without SSH there.)
- GHA/windows: make test tool installs a separate step.
- GHA/cygwin: enable OpenSSH server.
Skip `impacket`: it's compiling for 7 minutes then breaks.
Skip `stunnel` due to sluggish test run performance.
(This update is unrelated to Azure jobs.)
- GHA/linux: migrate Linux jobs from Azure CI.
- GHA/linux: migrate scanbuild job from Azure CI.
- GHA/linux: enable libssh2 in a job. Also enable valgrind.
- CI/windows: enable SSPI in two jobs.
- CI/windows: disable zlib in one more job.
- CI/windows: improve `if` condition checking GnuTLS.
- CI/windows: ignore SFTP/SCP tests as necessary.
- universally ignore SCP tests, they fail everywhere.
- ignore test 612.
- ignore test 613 616 618 with MSYS2 mingw-w64.
- ignore test 614 with libssh.
- ignore all SFTP with MSYS2 native.
- ignore all SFTP with vcpkg with `libssh2[core,zlib]`.
- ignore a couple of SFTP tests with MSYS2 mingw-w64.
(This matches settings on Azure CI.)
- GHA/windows: ignore failing 1451 'Basic SMB request' test for
old mingw-w64 7.3.0 (but not for 9.5.0!):
```
2024-09-11 21:45:59,738 ERROR smbComNegotiate: b'NT LM 0.12\x00' is not in list
[...]
curl: (7) Could not connect to server
[...]
FAIL 1451: 'Basic SMB request' SMB
```
Ref: https://github.com/curl/curl/actions/runs/10816280746/job/30007130770#step:13:3546
- CI/Azure: delete, now moved to GHA.

sshserver:

- sshserver: fix permissions for SSH host key on Windows, allowing sshd
to launch.
- sshserver: fix initializing config paths with Cygwin/MSYS2 sshd.
- sshserver: fix initializing config paths in parallel builds.
- sshserver: delete redundant `DenyUsers`. This also opens the way
to allow multiple usernames.
- sshserver: fix `AllowUsers` for GHA/windows, by allowing the
domainless username again.
Follow-up to 3ee7c676ec8ef32e3a9cb4d0fb2929a8335d58db #5721
- sshserver: fix `Deprecated option` warnings in `sshd_config`:
```
D:/a/curl/curl/bld/tests/log/2/server/curl_sshd_config line 7: Deprecated option AuthorizedKeysFile2
D:/a/curl/curl/bld/tests/log/2/server/curl_sshd_config line 25: Deprecated option KeyRegenerationInterval
D:/a/curl/curl/bld/tests/log/2/server/curl_sshd_config line 35: Deprecated option RhostsRSAAuthentication
D:/a/curl/curl/bld/tests/log/2/server/curl_sshd_config line 36: Deprecated option RSAAuthentication
D:/a/curl/curl/bld/tests/log/2/server/curl_sshd_config line 37: Deprecated option ServerKeyBits
D:/a/curl/curl/bld/tests/log/2/server/curl_sshd_config line 41: Deprecated option UseLogin
```
- sshserver: fix `Deprecated option` warnings in `ssh_config` with
Cygwin/MSYS2.
- sshserver: fix dumping config files due to the filenames missing their
full paths.
- sshserver: add workaround to make `logmsg` messages visible.
Before this patch they only went to a file and never shown.

runtests:

- runtests: log details when these Windows commands are called:
`handle`, `taskkill`, `tasklist`.
- runtests: add documentation links to Windows tools:
`handle`, `taskkill`, `tasklist`, `icacls`.
- runtests: add `-t` (kill whole tree) option to `taskkill` in
`servers.pm`, syncing it with the other `taskkill` call.
Follow-up to bc72a78a11764558639131d51fa8e7c81ee1e113 #14488
- runtests: show warning if Sysinternals `handle` tool is missing.
- runtests: drop Windows XP Home compatibility `tskill` call.
The call was made on all Windows versions. It's possibly overkill to
do this, because XP Home is probably rarely used for running curl
tests these days. In case it's needed, it'd be better to put it under
an explicit option.
- runtests: show Perl version and path.

Fix/silence fallouts:

- unit2603: fix building with disabled HTTP support.
- unit2604: silence `-Woverlength-strings` warnings in C89 mode.
- test437, test1614: fix to pass with no-IPv6 builds.

Closes #14859

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trace: make tracing available in non-debug builds

Add --trace-config to curl

Add curl_global_trace() to libcurl

Closes #11421

http2: support HTTP/2 to forward proxies, non-tunneling

- with `--proxy-http2` allow h2 ALPN negotiation to
forward proxies
- applies to http: requests against a https: proxy only,

http2: support HTTP/2 to forward proxies, non-tunneling

- with `--proxy-http2` allow h2 ALPN negotiation to
forward proxies
- applies to http: requests against a https: proxy only,
as https: requests will auto-tunnel
- adding a HTTP/1 request parser in http1.c
- removed h2h3.c
- using new request parser in nghttp2 and all h3 backends
- adding test 2603 for request parser
- adding h2 proxy test cases to test_10_*

scorecard.py: request scoring accidentally always run curl
with '-v'. Removed that, expect double numbers.

labeller: added http1.* and h2-proxy sources to detection

Closes #10967

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