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.

Start by locating the macOS UI and synchronization CreateRequest construction; the issue does not name files or tests. Trace how synchronization configuration is presented, then determine how the ignore syntax, default ignores, ignores, and VCS mode options should be exposed and verify that each is included in the request.

Scritto dal modello di indicizzazione a partire dal testo della issue.