Disable formatting for more macros.

Follow-on to #743. Disables formatting for `#_sourceLocation` and `@Tag`.
Although I haven't seen either in a sample/spindump, every little bit counts and
neither of these macros needs the formatting to build correctly.

Author: grynspan

Sources/TestingMacros/SourceLocationMacro.swift

@@ -22,4 +22,8 @@ public struct SourceLocationMacro: ExpressionMacro, Sendable {
   ) throws -> ExprSyntax {
     createSourceLocationExpr(of: macro, context: context)
   }
+
+  public static var formatMode: FormatMode {
+    .disabled
+  }
 }

Sources/TestingMacros/TagMacro.swift

@@ -102,4 +102,8 @@ public struct TagMacro: PeerMacro, AccessorMacro, Sendable {
     }
     return []
   }
+
+  public static var formatMode: FormatMode {
+    .disabled
+  }
 }