[Feature][SDK] Transform SQL support temporal functions(Including form_unixtime, unix_timestamp and to_timestamp)

[yfsn666]

Description

Enable transform SQL to support the following FlinkSQL temporal functions:

• form_unixtime(numeric[, string]): returns a representation of the numeric argument as a value in string format (default is ‘yyyy-MM-dd HH:mm:ss’). numeric is an internal timestamp value representing seconds since ‘1970-01-01 00:00:00’ UTC, such as produced by the UNIX_TIMESTAMP() function.
• unix_timestamp(): returns current Unix timestamp in seconds.
• unix_timestamp(string1[, string2]): converts date time string string1 in format string2 (by default: yyyy-MM-dd HH:mm:ss if not specified) to Unix timestamp (in seconds).
• to_timestamp(string1[, string2]): converts date time string string1 with format string2 (by default: ‘yyyy-MM-dd HH:mm:ss’) under the ‘UTC+0’ time zone to a timestamp.

Parent issue:
#10022

Use case

No response

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• Yes, I am willing to submit a PR!

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