V2: Generate comments for feature options

[timostamm]

When a field option like jstype is set in Protobuf, we include it in the JSDoc block of the generated code. For example:

/**
 * @generated from field: int64 foo = 1 [jstype = JS_STRING];
 */
foo: string;

With this change, we also include edition features. For example:

/**
 * @generated from field: string foo = 1 [features.field_presence = IMPLICIT];
 */
foo: string;

Features can also be set as file options. We include them in the preamble comment:

// @generated from file test/features.proto (package test, edition 2023)
// option features.field_presence = EXPLICIT;

Some features can be set as message or enum options. These features are included in the JSDoc block for the generated type:

/**
 * @generated from enum test.SomeEnum
 * @generated with option features.enum_type = OPEN
 */
export enum SomeEnum {