Improved efficiency of Differ.

[oskarwrobel]

Suggested merge commit message (convention)

Fix: Fixed problem with handling very large text nodes. Part of ckeditor/ckeditor5#1875.

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Additional information

For example – encountered issues, assumptions you had to make, other affected tickets, etc.

[coveralls]

Coverage remained the same at 100.0% when pulling 7455550 on t/ckeditor5/1875 into 0a268ab on master.

[pjasiun]

Thanks to this fix there is no error but the editor still works super slow with the content provided in the ticket. However, it is not a scope of this PR.

[oskarwrobel]

Unfortunately, the test takes too long for CI and it leads to a timeout. I need to remove unit tests for this change.

[Mgsy]

LGTM. It doesn't throw anymore, however, as @pjasiun mentioned, after pasting the content from the sample file, it's still impossible to use the editor because of low performance.

[Reinmar]

Did you try to use concat() too? Did you measure the performance of this solution?

[oskarwrobel]

Nope, I focused on making the editor not crash. The issue is still open for performance improvements.

[oskarwrobel]

Looks like concat may be faster:

https://jsperf.com/concat-vs-loop-differ/1