build: make `CURL_FORMAT_CURL_OFF_T[U]` work with mingw-w64 <=7.0.0

Add tweak for mingw-w64 when building tests/http/client programs to
avoid a bogus `-Wformat` warning when using mingw-

build: make `CURL_FORMAT_CURL_OFF_T[U]` work with mingw-w64 <=7.0.0

Add tweak for mingw-w64 when building tests/http/client programs to
avoid a bogus `-Wformat` warning when using mingw-w64 v7.0.0 or older.
The warning is bogus because these programs use curl's `printf()`
implementation that is guaranteed to support that format spec.

Add this for both CMake and autotools. (But only CMake is CI tested with
an old toolchain.)

Apply the workaround to `docs/examples`, and fix an example to use
curl's `printf()` with `CURL_FORMAT_CURL_OFF_T`.

Reintroduce curl `printf()` calls into `tests/http/client`, via #14625.
Also restore large number masks to a printf, changed earlier in #14382.

Follow-up to 232302f88a152a1d1722da9f69c383a766528918 #14382
Ref: https://github.com/curl/curl/pull/14625#issuecomment-2302361737

Closes #14640

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cmake: add Linux CI job, fix pytest with cmake

- extend existing Linux workflow with CMake support.
Including running pytest the first time with CMake.

- cmake: generate `test

cmake: add Linux CI job, fix pytest with cmake

- extend existing Linux workflow with CMake support.
Including running pytest the first time with CMake.

- cmake: generate `tests/config` and `tests/http/config.ini`.
Required for pytest tests.
Uses basic detection logic. Feel free to take it from here.
Also dump config files in a CI step for debugging purposes.

- cmake: build `tests/http/clients` programs.

- fix portability issues with `tests/http/clients` programs.
Some of them use `getopt()`, which is not supported by MSVC.
Fix the rest to compile in CI (old-mingw-w64, MSVC, Windows).

- GHA/linux: add CMake job matching an existing autotools one.

- GHA/linux: test `-DCURL_LIBCURL_VERSIONED_SYMBOLS=ON`
in the new CMake job.

- reorder testdeps to build server, client tests first and then
libtests and units, to catch errors in the more complex/unique
sources earlier.

- sort list in `tests/http/clients/Makefile.inc`.

Closes #14382

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http2: upgrade tests and add fix for non-existing stream

- check in h2 filter recv that stream actually exists
and return error if not
- add test for parallel, extreme h2 upgrades

http2: upgrade tests and add fix for non-existing stream

- check in h2 filter recv that stream actually exists
and return error if not
- add test for parallel, extreme h2 upgrades that fail if
connections get reused before fully switched
- add h2 upgrade upload test just for completeness

Closes #11563

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