Use metrics.width for spaces in writeTextToCanvas

[ebogo1]

Fixes a mistake from #9765 where I hardcoded space characters to return a width of 0 in the new measureText function. This fix matches the implementation of the third party measureText that used to be in main and fixes the spacing bug seen in the CMZL reference properties sandcastle -

PR branch:

1.84:

main:

[cesium-concierge]

Thanks for the pull request @ebogo1!

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