Support scheme-agnostic projects (#486)

This adds changes to support loading project dependencies in non-file based projects.

The design for this feature can be found in SPICE-0005: https://github.com/apple/pkl-evolution/pull/6

Changes:
* Consider all imports prefixed with `@` as dependency notation.
* Bugfix: fix resolution of glob expressions in a local dependency.
* Adjust pkl.Project:
  - Allow local dependencies from a scheme-local paths.
  - Disallow certain evaluator settings if not loaded as a file-based module.
* Breaking API change: `ProjectDependenciesManager` constructor now requires `ModuleResolver` and `SecurityManager`.

pkl-executor/src/test/kotlin/org/pkl/executor/EmbeddedExecutorTest.kt

@@ -478,7 +478,7 @@ class EmbeddedExecutorTest {
     )
     val result = executor.evaluatePath(pklFile) {
       allowedModules("file:", "package:", "projectpackage:", "https:")
-      allowedResources("prop:", "package:", "projectpackage:", "https:")
+      allowedResources("file:", "prop:", "package:", "projectpackage:", "https:")
       moduleCacheDir(cacheDir)
       projectDir(projectDir)
     }