[pdsl] Adjust .gitignore and workspace Cargo.toml for latest renamings

.gitignore

 # Ignore build artifacts from the local tests sub-crate.
 /target/
-/pdsl_tests/target/
-/pdsl_core/target/
-/pdsl_derive/target/
+/core/target/
+/derive/target/
 /examples/**/target/
-
 /design/
-/pdsl_tests/examples/
 
 # Ignore backup files creates by cargo fmt.
 **/*.rs.bk

Cargo.toml

 [workspace]
 
 members = [
-	"pdsl_core",
-	# "pdsl_derive",
+	"core",
+	# "derive",
 ]
 exclude = [
 	"examples/",