Add Support for TRY_CAST in PostgreSQL Dialect

[bjp232004]

Describe the bug
We are using the PostgreSQL dialect to verify SQL queries. Along with that, we support various SQL functions, and one of the functions we use is TRY_CAST. However, PostgreSQL dialect natively supports CAST but does not support TRY_CAST.

We need a way to add support for the TRY_CAST function, even though PostgreSQL itself does not have native support for this function.

Database Engine
PostgreSQL + Additional Custom Function

To Reproduce
-the SQL that be parsed: select TRY_CAST(field1 as INT) from table
-the node-sql-parser version: 5.2.0
Node Version: 20+

Expected behavior
TRY_CAST should function similarly to other databases that support it, where it tries to cast the value to the target type and returns NULL if the cast fails.

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Additional context
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