Use AbsolutePath.asURL instead of creating a new URL from the path string (#8159)

Use `AbsolutePath.asURL` instead of creating a new URL from the path
string.

### Motivation:

The original PR that added `resources`, `ignored`, and `other` files to
`BuildTarget` should have used `AbsolutePath.asURL` instead of creating
a new URL from the path string. This PR fixes that in order to maintain
a single location where absolute paths can be converted to URLs.

### Modifications:

I've replaced the `AbsolutePath` to `URL` mappings in `SourceKitLSPAPI`
with calls to `AbsolutePath.asURL`.

### Result:

This PR does not have an affect on the functionality of Swift Package
Manager.

Author: matthewbastien

Sources/SourceKitLSPAPI/BuildDescription.swift

@@ -82,15 +82,15 @@ private struct WrappedClangTargetBuildDescription: BuildTarget {
     }
 
     var resources: [URL] {
-        return description.resources.map { URL(fileURLWithPath: $0.path.pathString) }
+        return description.resources.map(\.path.asURL)
     }
 
     var ignored: [URL] {
-        return description.ignored.map { URL(fileURLWithPath: $0.pathString) }
+        return description.ignored.map(\.asURL)
     }
 
     var others: [URL] {
-        return description.others.map { URL(fileURLWithPath: $0.pathString) }
+        return description.others.map(\.asURL)
     }
 
     public var name: String {
@@ -129,21 +129,21 @@ private struct WrappedSwiftTargetBuildDescription: BuildTarget {
     }
 
     var sources: [URL] {
-        return description.sources.map { URL(fileURLWithPath: $0.pathString) }
+        return description.sources.map(\.asURL)
     }
 
     var headers: [URL] { [] }
 
     var resources: [URL] {
-        return description.resources.map { URL(fileURLWithPath: $0.path.pathString) }
+        return description.resources.map(\.path.asURL)
     }
 
     var ignored: [URL] {
-        return description.ignored.map { URL(fileURLWithPath: $0.pathString) }
+        return description.ignored.map(\.asURL)
     }
 
     var others: [URL] {
-        return description.others.map { URL(fileURLWithPath: $0.pathString) }
+        return description.others.map(\.asURL)
     }
 
     func compileArguments(for fileURL: URL) throws -> [String] {

Sources/SourceKitLSPAPI/PluginTargetBuildDescription.swift

@@ -36,21 +36,21 @@ struct PluginTargetBuildDescription: BuildTarget {
     }
 
     var sources: [URL] {
-        return target.sources.paths.map { URL(fileURLWithPath: $0.pathString) }
+        return target.sources.paths.map(\.asURL)
     }
 
     var headers: [URL] { [] }
 
     var resources: [URL] {
-        return target.underlying.resources.map { URL(fileURLWithPath: $0.path.pathString) }
+        return target.underlying.resources.map(\.path.asURL)
     }
 
     var ignored: [URL] {
-        return target.underlying.ignored.map { URL(fileURLWithPath: $0.pathString) }
+        return target.underlying.ignored.map(\.asURL)
     }
 
     var others: [URL] {
-        return target.underlying.others.map { URL(fileURLWithPath: $0.pathString) }
+        return target.underlying.others.map(\.asURL)
     }
 
     var name: String {