feat: add MD5 hash UDF

[derekjn]

Description

Adds a new MD5 UDF that takes a string as input and outputs the hex-encoded MD5 hash of the string.

Testing done

• Unit tests
• Functional tests
• Historical query plan

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[cbsmith]

Not to look a gift horse in the mouth, but is there a reason to add MD5 instead of modern secure hashes like SHA-2 that are still considered safe to use for security purposes?

[derekjn]

Not to look a gift horse in the mouth, but is there a reason to add MD5 instead of modern secure hashes like SHA-2 that are still considered safe to use for security purposes?

Hey @cbsmith! MD5 was added specifically due to a number of users who require it. Do you require a SHA-2 built-in?