tools/cmd/gen: Add more utilities to the templates

* Ensure that copyright years are preserved when regenerating.
* Add 'Split' function which maps to strings.Split.
* Add 'Scramble' function with messes with a string.
* Add 'Import' function which allows templates to be imported, allowing
  for reusable macros.

Change-Id: Ib77f59a989cf55addcced3e337c9031062a83470
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/97149
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

tools/src/tint/intrinsic/sem/sem.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"sort"
 
+	"dawn.googlesource.com/dawn/tools/src/container"
 	"dawn.googlesource.com/dawn/tools/src/tint/intrinsic/ast"
 )
 
@@ -39,6 +40,16 @@ type Sem struct {
 	UniqueParameterNames []string
 }
 
+// Enum returns the enum with the given name
+func (s *Sem) Enum(name string) *Enum {
+	for _, e := range s.Enums {
+		if e.Name == name {
+			return e
+		}
+	}
+	return nil
+}
+
 // New returns a new Sem
 func New() *Sem {
 	return &Sem{
@@ -69,6 +80,26 @@ func (e *Enum) FindEntry(name string) *EnumEntry {
 	return nil
 }
 
+// PublicEntries returns the enum entries that are not annotated with @internal
+func (e *Enum) PublicEntries() []*EnumEntry {
+	out := make([]*EnumEntry, 0, len(e.Entries))
+	for _, entry := range e.Entries {
+		if !entry.IsInternal {
+			out = append(out, entry)
+		}
+	}
+	return out
+}
+
+// NameSet returns a set of all the enum entry names
+func (e *Enum) NameSet() container.Set[string] {
+	out := container.NewSet[string]()
+	for _, entry := range e.Entries {
+		out.Add(entry.Name)
+	}
+	return out
+}
+
 // EnumEntry is an entry in an enumerator
 type EnumEntry struct {
 	Enum       *Enum