eth: add optional v value for 2930 and 1559 txs (#446)

It looks like many clients are currently either not returning yParity or returning both v and yParity. To align the spec with this, I'm proposing we add an optional (but deprected) v value for 2930 and 1559 txs. This way clients can continue use it and tooling can have some space to upgrade to yParity.

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Co-authored-by: Felix Lange <fjl@twurst.com>

Author: lightclient

src/schemas/transaction.yaml

@@ -181,6 +181,10 @@ Transaction1559Signed:
           title: yParity
           description: The parity (0 for even, 1 for odd) of the y-value of the secp256k1 signature.
           $ref: '#/components/schemas/uint'
+        v:
+          title: v
+          description: For backwards compatibility, `v` is optionally provided as an alternative to `yParity`. This field is DEPRECATED and all use of it should migrate to `yParity`.
+          $ref: '#/components/schemas/uint'
         r:
           title: r
           $ref: '#/components/schemas/uint'
@@ -202,6 +206,10 @@ Transaction2930Signed:
           title: yParity
           description: The parity (0 for even, 1 for odd) of the y-value of the secp256k1 signature.
           $ref: '#/components/schemas/uint'
+        v:
+          title: v
+          description: For backwards compatibility, `v` is optionally provided as an alternative to `yParity`. This field is DEPRECATED and all use of it should migrate to `yParity`.
+          $ref: '#/components/schemas/uint'
         r:
           title: r
           $ref: '#/components/schemas/uint'