Add transpilation support for DECRYPT, and test cases for DECRYPT

[fivetran-ashashankar]

marking decrypt transpilation unsupported because duckdb has no support for the function

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:RD-1069381-transpile-decrypt, sqlglot version: RD-1069381-transpile-decrypt)
• baseline (main, sqlglot version: 0.0.1.dev1)

By Dialect

dialect	main	sqlglot:RD-1069381-transpile-decrypt	transitions	links
bigquery -> bigquery	22925/22930 passed (100.0%)	21255/21255 passed (100.0%)	No change	full result / delta
bigquery -> duckdb	1304/1674 passed (77.9%)	0/0 passed (0.0%)	Results not found	full result / delta
snowflake -> duckdb	1521/2678 passed (56.8%)	0/0 passed (0.0%)	Results not found	full result / delta
snowflake -> snowflake	65927/65927 passed (100.0%)	63028/63028 passed (100.0%)	No change	full result / delta
databricks -> databricks	1370/1370 passed (100.0%)	1370/1370 passed (100.0%)	No change	full result / delta
postgres -> postgres	6042/6042 passed (100.0%)	6042/6042 passed (100.0%)	No change	full result / delta
redshift -> redshift	7101/7101 passed (100.0%)	7101/7101 passed (100.0%)	No change	full result / delta

Overall

main: 107722 total, 106190 passed (pass rate: 98.6%), sqlglot version: 0.0.1.dev1

sqlglot:RD-1069381-transpile-decrypt: 98796 total, 98796 passed (pass rate: 100.0%), sqlglot version: RD-1069381-transpile-decrypt

Transitions:
No change

Dialect pair changes: 0 previous results not found, 2 curent results not found

✅ 17 test(s) passed