fix(heatmap): fix labels not in calendar range are unexpectedly displayed

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Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Fix the bug that labels not in the calendar range are unexpectedly displayed, as a supplement fix of #12991.

Demo

Fixed issues

Fix #20690

Details

Before: What was the problem?

After: How does it behave after the fixing?

Document Info

One of the following should be checked.

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

ZRender Changes

• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

Please refer to test/calendar-heatmap2.html

Others

Merging options

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

Other information

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The changes brought by this PR can be previewed at: https://echarts.apache.org/examples/editor?version=PR-20699@2872e5c