Memory Leak

[KatieWoe]

For phetsims/qa#870. Seen on Win 11 Chrome
These are the results from the memory test. It seems to indicate a memory leak somewhere.

[jessegreenberg]

Thanks @KatieWoe. I wonder if this is caused by recent string -> StringProperty conversions in #350.

[samreid]

@AgustinVallejo and @jbphet will coordinate on this on Jan 4, thanks!

[samreid]

@jonathanolson also corrected a memory leak in font awesome nodes in this commit: phetsims/sherpa@68ffa3d

I tested fuzzing for 20 minutes and it seems stable. I think this issue is ready to close.

Though I am not sure the full timeline or steps to recreate a table like #362 (comment). @AgustinVallejo do you think this issue can be closed? Do you want a double check by @KatieWoe ?

[samreid]

I got another reading at 30 minutes, so I'm feeling more confident about this:

[KatieWoe]

Memory test looks good in rc.2