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.

まず、macOS UI と同期用の CreateRequest の構築箇所を特定します。この issue ではファイルやテストが指定されていません。同期設定がどのように表示されるかを追跡し、ignore 構文、デフォルトの ignore、ignore、VCS モードの各オプションをどのように公開すべきかを判断して、それぞれがリクエストに含まれていることを確認します。

索引モデルが issue の本文から書いたものです。