[EPIC] Support try_* functions which always return NULL instead of runtime errors

[advancedxy]

Spark adds a lot of try_* functions in the recent two years, which always return NULL instead of runtime errors. The list is as follows:

• try_add
• try_divide
• try_subtract
• try_multiply
• try_element_at
• try_avg
• try_sum
• try_to_binary
• try_to_timestamp
• try_aes_decrypt
• try_reflect (cannot be supported in Comet?)
• try_cast (part of [EPIC] Spark-compatible cast / try_cast operations #286)

We should add support to these functions too. It could be implemented in Comet first then contributed back to upstream DataFusion.

Originally posted by @viirya in #277 (comment)

[andygrove]

I added try_cast to the list, with a link to the cast epic