Add analyze imports libs (SPICE-0001) (#695)

This adds a new feature to build a dependency graph of Pkl programs, following the SPICE outlined in https://github.com/apple/pkl-evolution/pull/2.

It adds:
* CLI command `pkl analyze imports`
* Java API `org.pkl.core.Analyzer`
* Pkl stdlib module `pkl:analyze`
* pkl-gradle extension `analyze`

In addition, it also changes the Gradle plugin such that `transitiveModules` is by default computed from the import graph.

stdlib/analyze.pkl

@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+/// A library for statically analyzing Pkl modules.
+///
+/// These tools differentiate from [pkl:reflect][reflect] in that they parse Pkl modules, but do not
+/// execute any code within these modules.
+@Since { version = "0.27.0" }
+@ModuleInfo { minPklVersion = "0.27.0" }
+module pkl.analyze
+
+// used by doc comments
+import "pkl:reflect"
+
+/// Given a set of Pkl module URIs, returns a graph of imports declared by these modules.
+///
+/// The resulting graph includes transitive imports.
+external function importGraph(moduleUris: Set<Uri>): ImportGraph
+
+/// The graph of imports declared (directly and transitively) by the modules passed to
+/// [importGraph()].
+class ImportGraph {
+  /// The imports declared within a Pkl program.
+  ///
+  /// Each entry maps a module URI to the set of imports declared in that module.
+  ///
+  /// The set of all modules in the graph can be obtained via its [keys][Map.keys].
+  imports: Map<Uri, Set<Import>>
+
+  /// Mappings of modules from their in-language URI, to their resolved URI.
+  ///
+  /// A module's in-language URI is the form used within Pkl source code.
+  /// For example, modulepath-based modules have form `modulepath:/path/to/my/module.pkl`.
+  ///
+  /// A module's resolved URI is the form used to load the module's contents.
+  /// The same modulepath module might have form
+  /// `jar:file:///path/to/file.zip!/path/to/my/module.pkl` if Pkl run with
+  /// `--module-path /path/to/file.zip`.
+  ///
+  /// Dependency-notation imports, such as `"@myPackage/myModule.pkl"`, are represented as
+  /// in-language URIs with scheme `projectpackage:`.
+  /// In the case of local project dependenecies, they will be local URIs resolved from the project
+  /// file URI (in normal cases, `file:` URIs).
+  resolvedImports: Map<Uri, Uri>(keys == imports.keys)
+}
+
+/// An import as declared inside a module.
+class Import {
+  /// The absolute (in-language) URI of the import.
+  ///
+  /// Dependency notation URIs (such as `import "@foo/bar"`) are resolved to package URIs with
+  /// scheme `projectpackage:`.
+  uri: Uri
+}