feat: add environment solution sync

[zekelinAlex]

Adds txc environment solution sync, our take on pac solution sync for pulling a
solution back into local source without the git churn.

Dataverse rewrites plugin-assembly paths on export (PluginAssemblies/{Name}-{GUID}/...)
and ships the compiled binaries, and neither matches how we keep source. So after unpack
this flattens the paths back to PluginAssemblies/{Name}.dll, fixes the <FileName>, and
drops the binaries that are built locally so they stay out of git.

The project file decides what gets dropped. A Plugin or WorkflowActivity
<ProjectReference> means its .dll is built here, so we keep the .data.xml and skip the
binary. A ScriptLibrary reference works the same way for the built .js web resource. A
plugin that just lives in the environment, with no reference, keeps its binary.

To stay safe it unpacks into a temp folder and merges only the solution component folders,
so your .csproj, bin and obj are never touched.

Closes #57.