(de)serialization of transactions with certain data in the ExtraField fail 
#### (de)serialization of transactions with MergeMining in the ExtraField fail because Monero encodes the size of the field 

https://github.com/monero-project/monero/blob/fc907a957078cae2dc68348886a33363848dd089/src/cryptonote_basic/tx_extra.h#L179

some examples of these transactions: 
 [36817336e72ecf7adcff92815de96a0893c1ef777701f1386ebce5f7d9272151](https://xmrchain.net/tx/36817336e72ecf7adcff92815de96a0893c1ef777701f1386ebce5f7d9272151/1)
[8b1daf9c85520ceee2e9ae5f7e66f9e72d1967f5c537180887865fb21fffbb45](https://xmrchain.net/tx/8b1daf9c85520ceee2e9ae5f7e66f9e72d1967f5c537180887865fb21fffbb45)
[1323c9e102253577690d75f8f77872ffada1c63c96dd3156330896d6e40207b2](https://xmrchain.net/tx/1323c9e102253577690d75f8f77872ffada1c63c96dd3156330896d6e40207b2/1)



#### (de)serialization of transactions with MysteriousMinerGate fail for the same reason and because it shouldn't be a string 

this is the raw hex of a transaction with MysteriousMinerGate in the ExtraField:
 
>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
 
~~#### (de)serialization of transactions with AdditionalPublickKeys fail because the field should just be PublicKey not a Vec
example of a transaction with AdditionalPublickKeys:
[23fbc9f5b8ac1b6f896756c4a1382658daf1e8d371c1e01c5baf66c1fbaf39bd](https://xmrchain.net/tx/23fbc9f5b8ac1b6f896756c4a1382658daf1e8d371c1e01c5baf66c1fbaf39bd/1)~~

although these errors can be fixed, as far as I know the extra field is a "free zone" for wallets to put whatever data they want. So I think it would be better to not error if the transactions extra field can't be de-serialized and instead just return the extra field raw. 
 