Left pad odd length hex strings

[adjeiv]

Fixes dolthub/dolt#6351
If hex string v is of odd length, prepend an "0" before passing it to Go's DecodeString.
I've changed the implementation to use DecodeString, but if keeping this as a byte array is preferred, I'll switch back.

[fulghum]

Thank you for this contribution @adjeiv! 🙏 Your fix looks really great.

Could you please add a really quick query test (e.g. select 0x12345) to this file:

go-mysql-server/enginetest/queries/queries.go

Line 743 in f5d1232

var QueryTests = []QueryTest{

After that, this looks good to merge!

(I see there's one CI check that's failing for import ordering, but it doesn't seem related, since your changes didn't touch the imports, so don't worry about that one.)

[fulghum]

Looks perfect! Thank you so much @adjeiv! 🙏

Let us know if there's anything we can do to help you in your use of go-mysql-server and Dolt!