fix(tooltip): find closest for band scale

[pearmini]

close: #5543

存在问题

双轴图，存在 Item Mark（比如 Interval）和 Series Mark（比如 Line）的时候会有问题：

• 没有拾取到 line 到数据：

• 没有拾取到 interval 的数据：

出现原因

• Series Mark 默认不会去拾取超出范围的元素的数据
• Item Mark 默认只会拾取包含鼠标位置的元素的数据

解决办法

当是 Band 比例尺的时候，Series tooltip 找到最近的元素。

TODO

• code
• docs
• examples
• tests

[coveralls]

Pull Request Test Coverage Report for Build 6233042899

• 17 of 22 (77.27%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 88.468%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/interaction/tooltip.ts	17	22	77.27%

Totals
Change from base Build 6230758416:	-0.01%
Covered Lines:	9977
Relevant Lines:	10916

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💛 - Coveralls