[ecm] Force vcpkg filesystem, revise downstream

[dg0yt]

• Don't put data into /bin.
  Simply use the same layout as for non-win32, so that portfiles don't need to care.
• Put "libexec" tools file to /bin. Simplifies moving them to /tools/<port>.
  (Actually these are candidates for /manual-tools, but it is out of scope for this PR.)
• Put plugins to /plugins, and QML to /qml.
• Prevent pointless generationg of .clang-format in source directories of ports.

Revise and cleanup downstream ports which need changes. (Not changing ports which don't need changes. But revise with proper inspection of actual dependencies.)

[MonicaLiu0311]

Is there any new progress?

[dg0yt]

Please leave this draft open unless somebody takes over.

[SunBlack]

I had in my PR didn't changed it to this, as e.g., this module uses the network module of Qt and therefore support of OpenSSL for https could be necessary, or?

[dg0yt]

The network module is always installed.
openssl isn't the only TLS backend.
And openssl is a default feature. Users get openssl by default. This line just enables a different choice.
So IMO default features are not necessary unless some other code says openssl is required. In that it case it should be added as an explicit feature of the dependency.

[SunBlack]

@dg0yt Once you have the CI up and running, could you see if you can include the upgrade to 6.22 (so there is no need to maybe update the patches again a few days after this PR is getting merged)? I saw in #49541 that @Neumann-A patches kf6archive there. However, this patch is unnecessary if we update the port to at least 6.20 (see commit) - but then we need at least the same ECM version.

[dg0yt]

I don't want to add more changes.

Note the existing kf6archive/kf5archive pattern is different from what happened with kf5diagram in #49313.

[SunBlack]

Seems the CI is already in the weekend 😅

##[error]We stopped hearing from agent CPPMAC-ARM64-09. Verify the agent machine is running and has a healthy network connection. Anything that terminates an agent process, starves it for CPU, or blocks its network access can cause this error. For more information, see: https://go.microsoft.com/fwlink/?linkid=846610

[vicroms]

clever!