addNamedMetadataAssumeCapacity

fn addNamedMetadataAssumeCapacity(self: *Builder, name: String, operands: []const Metadata) void {
    assert(name != .none);
    const extra_index: u32 = @intCast(self.metadata_extra.items.len);
    self.metadata_extra.appendSliceAssumeCapacity(@ptrCast(operands));

    const gop = self.metadata_named.getOrPutAssumeCapacity(name);
    gop.value_ptr.* = .{
        .index = extra_index,
        .len = @intCast(operands.len),
    };
}