GenerateNetFxTransientDependencies does not remove packages

[RassK]

Bug Report

Nuke action GenerateNetFxTransientDependencies does not update dependencies correctly. When packages are updated and the updated version removes dependencies, GenerateNetFxTransientDependencies does not remove overleft package references.

Reproduce

Use my branch #4486 and update OpenTelemetry.OpAmp.Client from 0.1.0-alpha.1 to 0.1.0-alpha.2

CC: @iskiselev

[RassK]

Wondering if the fix could simply empty the list and regenerate it fully?

[iskiselev]

GenerateNetFxTransientDependencies have been reworked a lot in #4505.
It was not able to remove any unused PackageReference/PackageVersion before my change, if I read code correctly. After my change situation have improved a little bit: we still have not required PackageVersion in Directory.Packages.props, but there is no PackageReference for transitive packages anymore, so that PackageVersion are not used - no binaries from them placed in output. It works as: if you need package (have PackageReference or through transitive dependency) - please use specified version.

Fix is possible and should be easy, though a little bit harder than just regenerate it fully - I will prepare PR to do it once have some time.