fix(toolbox): fix the bug of overriding title when click the stack button

[pingf]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

fix bug of overriding the button title of the tool box

currently, if we change the title of the magic-type button in the toolbox, it works as expected
however, if we click the button for stack view, all magic type buttons' titles revert to the default

Fixed issues

• Toolbox magic type title #12979

Details

Before: What was the problem?

to check this one, we need to do sth like this

toolbox: {
               ......
                magicType: {
                    show: true,
                    type: ['line', 'bar', 'stack'],
                    title: {
                        line: 'line view',
                        bar: 'bar view',
                        stack: 'stack view',
                        tiled: 'tiled view',
                    },
                },
             ......
}      

as stack and tiled are sth like a pair, we need to set the title for the tiled

but it only works if we never click the stack button,
once we click the button for stack, all titles revert to the the default chinese ones

After: How is it fixed in this PR?

the old code use title from ecModel as the base to override the new title
however, this disable the ability to override the title by users

In this PR, I change the logic to flip the title of stack and tiled when we click, and use model.option to get the title dynamically

newTitle = zrUtil.merge({
                stack: model.option.title.tiled,
                tiled: model.option.title.stack
            }, model.option.title)

and now it works as expected(tested on my local machine)

Usage

Are there any API changes?

• The API has been changed.

Related test cases or examples to use the new APIs

NA.

Others

Merging options

• Please squash the commits into a single one when merge.

Other information

as I didn't find an existing test file for this, and I'm not familiar with the test structure of new echarts,
I didn't submit a independent test file for this,
but I do think the changes in this PR won't bother the main logic and will not decrease code coverage.
thx to @pissang & @Ovilia
just pushed the visual test action file in the latest commit

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[echarts-bot]

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