Write valid leader without counting #527

[TobiasNx]

Instead of just appending the incoming leader elements by encode-marcmxl, this adds the static values for Pos: 00-04, 10-16, 20-23.

By using 0as default value for Pos: 00-04 and 12-16.

https://github.com/metafacture/metafacture-core/issues/527#issuecomment-2076585889

[blackwinter]

What's the point of doing the "easy" solution now that we already have the "hard" solution?

[TobiasNx]

The leader is always valid?

[TobiasNx]

I will put this on hold, the failing test hints that it is not as easy: issue336_createRecordWithTopLevelLeader_defaultMarc21Xml