Fix: pass dialect to MD5 func builder in generate_surrogate_key macro

[georgesittas]

Today we get the first behavior when using this macro in BigQuery, which is incorrect.

>>> from sqlglot import exp
>>> exp.func("MD5", exp.Literal.string(f"Original value")).sql("bigquery")
"TO_HEX(MD5('Original value'))"
>>> exp.func("MD5", exp.Literal.string(f"Original value"), dialect="bigquery").sql("bigquery")
"MD5('Original value')"

Context: https://tobiko-data.slack.com/archives/C0448SFS3PF/p1729531496678999

[mr-mcox]

Thank you for addressing this - it was causing me a bit of confusion!

[georgesittas]

Sure thing, appreciate the report!