Fix line break of subflow label on palette

[HiroyasuNishiyama]

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

If the label of a SUBFLOW contains a line break (\n ), the label may be displayed outside of the SUBFLOW as shown below.

This PR attempts to fix this.

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the forum/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[coveralls]

Coverage increased (+0.04%) to 68.548% when pulling 435917c on node-red-hitachi:fix-line-break-of-subflow-label into bebebaa on node-red:dev.

[knolleary]

If the subflow name is ABCDEFG\n HIJKLMN then I would expect the label in the palette to be displayed as:

ABCEDFG
HIJKLMN

And not to have the \n displayed in plain text.

[HiroyasuNishiyama]

Thank you for your advice.
I will try to fix to change \n to line break.
My concern on handling \n in a SUBFLOW template label similar to on workspace is that the node width is fixed on palette so SUBFLOW template does not get the expected line breaks.

Assuming node has width of 3 characters,

ABCD\n EFG\n HI

SUBFLOW label is displayed as follows:

ABC
D
EFG

HI

[HiroyasuNishiyama]

Fixed to handle line break (\n ) on palette.