Docs: Add 6.4 release notes

Update the SwiftPM documentation to include 6.4 release notes.

Also, move the Release notes from previous released over to the official
documentation target

Issue: radr://171094628

Author: bkhouri

Sources/PackageManagerDocs/Documentation.docc/Documentation.md

@@ -10,7 +10,7 @@ Organize, manage, and edit Swift packages.
 
 The Swift Package Manager lets you share your code as a package, depend on and use other shared packages, as well as build, test, document, and run your code.
 
-> Note: Swift Package Manager is previewing the Swift Build build system. Learn more [here](<doc:SwiftBuildPreview>).
+> Note: Swift Package Manager [introduced the Swift Build build system as a preview](<doc:SwiftBuildPreview>) in Swift 6.3, and [adopted it as the default build system ](<doc:SwiftBuildDefault>) in Swift 6.4.
 
 ## Topics
 
@@ -19,9 +19,11 @@ The Swift Package Manager lets you share your code as a package, depend on and u
 - <doc:GettingStarted>
 - <doc:IntroducingPackages>
 - <doc:PackageSecurity>
+- <doc:ReleaseNotes>
 
 ### Guides
 
+- <doc:SwiftBuildDefault>
 - <doc:SwiftBuildPreview>
 - <doc:CreatingSwiftPackage>
 - <doc:SettingSwiftToolsVersion>

Sources/PackageManagerDocs/Documentation.docc/GeneratingSBOMs.md

@@ -6,7 +6,7 @@ Create an inventory of components and dependencies using SBOM documents.
 
 Swift Package Manager generates Software Bill of Materials (SBOM) documents for Swift packages and products.
 
-Swift Package Manager currently supports two SBOM formats: CycloneDX and SPDX. 
+Swift Package Manager currently supports two SBOM formats: CycloneDX and SPDX.
 
 Generate SBOMs using either the [`swift build`](doc:SwiftBuild) command with SBOM flags or the dedicated [`swift package generate-sbom`](doc:PackageGenerateSBOM) subcommand.
 
@@ -26,9 +26,9 @@ swift build --build-system swiftbuild --sbom-spec cyclonedx --sbom-spec spdx
 The following examples generate SBOMs without using the Swift Build build backend. SBOMs generated without Swift Build may not be fully accurate, as build-time conditionals aren't applied to the SBOMs.
 
 ```bash
-swift build --sbom-spec cyclonedx
-swift build --sbom-spec spdx
-swift build --sbom-spec cyclonedx --sbom-spec spdx
+swift build --build-system native --sbom-spec cyclonedx
+swift build --build-system native --sbom-spec spdx
+swift build --build-system native --sbom-spec cyclonedx --sbom-spec spdx
 ```
 
 ### Use the package command to generates SBOMs

Sources/PackageManagerDocs/Documentation.docc/ReleaseNotes.md

@@ -0,0 +1,13 @@
+# Release Notes
+
+## Topics
+
+- <doc:6.4>
+- <doc:6.3>
+- <doc:5.9>
+- <doc:5.8>
+- <doc:5.7>
+- <doc:5.6>
+- <doc:5.5>
+- <doc:5.4>
+- <doc:5.3>