test: add SQL file tests for aes_encrypt, aes_decrypt, try_aes_decrypt

[andygrove]

Which issue does this PR close?

N/A. This adds test coverage only. Related: #4558.

Rationale for this change

The AES functions (aes_encrypt, aes_decrypt, try_aes_decrypt) had no Comet test coverage. They are RuntimeReplaceable and lower to a StaticInvoke of ExpressionImplUtils.aesEncrypt / aesDecrypt. This test pins down their current behavior in Comet.

What changes are included in this PR?

Adds spark/src/test/resources/sql-tests/expressions/misc/aes.sql, covering GCM (default), ECB, and CBC modes; 16/24/32-byte keys; column and literal arguments; NULL inputs; and try_aes_decrypt on invalid ciphertext. Because aes_encrypt uses a random IV for GCM/CBC (nondeterministic output), those cases are tested via round-trip (aes_decrypt(aes_encrypt(x, k), k) = x); ECB output is deterministic and compared directly.

Empirical finding: all three functions currently fall back to Spark. Comet's StaticInvoke serde only allowlists a few target methods (readSidePadding, isLuhnNumber, URL encode/decode), and aesEncrypt / aesDecrypt are not among them, so the plan reports Static invoke expression: aesEncrypt is not supported. All queries therefore use query spark_answer_only (results are still validated against Spark). When native support is added, they can be promoted to the default query mode.

How are these changes tested?

This PR is test-only. The file runs under CometSqlFileTestSuite. Verified locally:

./mvnw test -Dsuites="org.apache.comet.CometSqlFileTestSuite aes" -Dtest=none

Result: the discovered test file passes.