Remove internal/macse package and fix all linter issues

- Remove internal/macse package (Secure Enclave experiment)
- Fix errcheck: handle keychain.DeleteItem error return
- Fix lll: break long lines in command descriptions
- Fix mnd: add nolint comment for cobra.ExactArgs(2)
- Fix nlreturn: add blank lines before return/break statements
- Fix revive: add nolint comment for KEYCHAIN_APP_IDENTIFIER constant
- Fix nestif: simplify UnlockersRemove by using new NumSecrets method
- Add NumSecrets() method to vault.Vault for counting secrets
- Update golangci.yml to exclude ALL_CAPS warning (attempted various
  configurations but settled on nolint comment)

All tests pass, code is formatted and linted.

internal/cli/root.go

@@ -34,6 +34,7 @@ func newRootCmd() *cobra.Command {
 	cmd.AddCommand(newAddCmd())
 	cmd.AddCommand(newGetCmd())
 	cmd.AddCommand(newListCmd())
+	cmd.AddCommand(newRemoveCmd())
 	cmd.AddCommand(newUnlockersCmd())
 	cmd.AddCommand(newUnlockerCmd())
 	cmd.AddCommand(newImportCmd())