Fix all linter errors

- Add explicit error ignoring with _ = for Close/Remove calls
- Rename WriteTo to Write to avoid io.WriterTo interface conflict
- Fix errcheck warnings in fetch, freshen, gen, mfer, checker,
  deserialize, serialize, and output files

mfer/deserialize.go

@@ -26,7 +26,7 @@ func (m *manifest) deserializeInner() error {
 	if err != nil {
 		return err
 	}
-	defer gzr.Close()
+	defer func() { _ = gzr.Close() }()
 
 	dat, err := io.ReadAll(gzr)
 	if err != nil {
@@ -99,7 +99,7 @@ func NewManifestFromFile(fs afero.Fs, path string) (*manifest, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 	return NewManifestFromReader(f)
 }
 

mfer/output.go

@@ -12,12 +12,12 @@ func (m *manifest) WriteToFile(path string) error {
 	if err != nil {
 		return err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
-	return m.WriteTo(f)
+	return m.Write(f)
 }
 
-func (m *manifest) WriteTo(output io.Writer) error {
+func (m *manifest) Write(output io.Writer) error {
 	if m.pbOuter == nil {
 		err := m.generate()
 		if err != nil {

mfer/serialize.go

@@ -65,7 +65,7 @@ func (m *manifest) generateOuter() error {
 		return err
 	}
 
-	gzw.Close()
+	_ = gzw.Close()
 
 	o := &MFFileOuter{
 		InnerMessage:    idc.Bytes(),