runtests: generate certs dynamically, bump to EC-256, tidy up

Before this patch the curl repository and source tarball distribution
contained test certificates as binary blobs. Used by runtests.

Drop these certificates in favor of generating them dynamically as
part of the build process. Both via autotools and CMake.

As part of this, improve certificates, the generator script and process,
file layout, and fix any issue to make it work fast and smooth both in
CI and local builds.

Note, cert generator scripts require OpenSSL >=1.0.2
(or LibreSSL >=3.1.0). Generation requires POSIX shell, also with CMake.
Without a POSIX shell tests relying on TLS (and stunnel) will fail.

Details:

- build: generate certs as part of the test run process.
- build, tests: generate certs in the build directory.
- binarycheck: drop concept of known binary files with hashes.
- binarycheck: move binary check logic into spacecheck and drop this
  separate checker tool.
- build: fix to clean all cert files.
- autotools: fix to not run leaf cert generators in parallel. To avoid
  confusion when updating the revocation database and counter.
- scripts: drop `scripts` subdir, merge two scripts into one,
  auto-generate root cert, allow generating multiple leafs at once.
- scripts: switch to EC-256 keys (was: RSA-2048). For key size and perf.
- scripts: drop `-x` echo, text dumps, most other output. To avoid log
  noise and make it quicker in CI.
- scripts: make it non-RSA-specific.
- scripts: delete unused code.
- scripts: use POSIX shell shebang. Some envs don't have bash (Alpine).
- scripts: pass test pseudo-secrets via the command-line. To avoid:
  ```
  + openssl genrsa -out test-ca.key -passout fd:0 2048
  Invalid password argument, starting with "fd:"
  ```
- cmake: fix to launch generator scripts via the detected POSIX shell.
- cmake: fix `build-certs` rule to not depend on `SRPFILES`
  (`srp-verifier-*`).
- cmake: drop `EXCLUDE_FROM_ALL` for the cert subdir. It makes
  the Visual Studio generator miss to create the `clean-certs`,
  `build-certs` targets. No target depend on them, so they don't execute
  implicitly anyway. Fixes:
  ```
  MSBUILD : error MSB1009: Project file does not exist.
  Switch: clean-certs.vcxproj
  ```
- cmake: add `VERBATIM USES_TERMINAL` to `build-certs` target.
- GHA/linux: install openssl on Alpine, for the cert generator scripts.

Follow-up to 556f722fe3 #16593
Follow-up to fa461b4eff #14486

Closes #16824

.github/workflows/linux.yml

@@ -327,7 +327,7 @@ jobs:
             libssh2-dev zlib-dev brotli-dev zstd-dev libidn2-dev openldap-dev \
             heimdal-dev libpsl-dev c-ares-dev \
             py3-impacket py3-asn1 py3-six py3-pycryptodomex \
-            perl-time-hires openssh stunnel sudo git
+            perl-time-hires openssh stunnel sudo git openssl
 
       - name: 'cache bearssl'
         if: contains(matrix.build.install_steps, 'bearssl')