Allow installation of multiple platformDependencies artifacts into separate subdirectories

COIN-646 requested a feature to allow specifying a list of platform dependencies to allow stitching together a multi-abi Qt for Android.

That was implemented, but we need to ensure that the artifacts installed from those dependencies are not installed into the same path, so that files are not overridden.

My proposal would be to add 2 new flags to the artifact installation commands:
installHostDepsPerPlatformSubdir and installTargetDepsPerPlatformSubdir

Af the flag is set to true, then each platform dependency is unpacked into a subdir named by the platform dependency id.
If false, the default current behavior, install all deps into same location.

I'd also add an additional option that takes an env var name, which will be populated with a semicolon separate list of values, where each value is the absolute dir name of the unpacked platform dir.

Affected commands:
InstallSourceArchive
InstallBinaryArchive
InstallTestBinaryArchive
Possibly other conan ones?