Support setting file sync ignore patterns via the UI

A Synchronization `CreateRequest` allows specifying a configuration for alpha, beta, or both simultaneously.
These configurations include the following fields:
```
// Ignore configuration parameters (fields 31-60).

// IgnoreSyntax specifies the syntax and semantics to use for ignores.
// NOTE: This field is out of order due to the historical order in which it
// was added.
ignore.Syntax ignoreSyntax = 34;

// DefaultIgnores specifies the ignore patterns brought in from the global
// configuration.
// DEPRECATED: This field is no longer used when loading from global
// configuration. Instead, ignores provided by global configuration are
// simply merged into the ignore list of the main configuration. However,
// older sessions still use this field.
repeated string defaultIgnores = 31;

// Ignores specifies the ignore patterns brought in from the create request.
repeated string ignores = 32;

// IgnoreVCSMode specifies the VCS ignore mode that should be used in
// synchronization.
ignore.IgnoreVCSMode ignoreVCSMode = 33;
```
We'll need to expose these synchronization configuration options via the UI.

Beginne damit, die macOS-UI und die Konstruktion von CreateRequest für die Synchronisierung zu lokalisieren; in diesem Issue werden keine Dateien oder Tests genannt. Verfolge, wie die Synchronisierungskonfiguration dargestellt wird, ermittle dann, wie die Optionen für die Ignore-Syntax, die Standard-Ignores, Ignores und den VCS-Modus verfügbar gemacht werden sollen, und überprüfe, dass jede davon in der Anfrage enthalten ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.