BIP 174: Add test vectors for additional unsigned tx serialization

There are some edge cases with unsigned tx serialization, so this adds
test vectors for them. Specifically, an unsigned tx with witness
serialization is invalid, a transaction with 0 inputs and 0 outputs is
valid, and a transaction with 0 inputs and non-0 outputs is valid.

Author: achow101

bip-0174.mediawiki

@@ -830,6 +830,10 @@ The following are invalid PSBTs:
 ** Bytes in Hex: <pre>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</pre>
 ** Base64 String: <pre>cHNidP8BAHMCAAAAATAa6YblFqHsisW0vGVz0y+DtGXiOtdhZ9aLOOcwtNvbAAAAAAD/////AnR7AQAAAAAAF6kUA6oXrogrXQ1Usl1jEE5P/s57nqKHYEOZOwAAAAAXqRS5IbG6b3IuS/qDtlV6MTmYakLsg4cAAAAAAAEBHwDKmjsAAAAAFgAU0tlLZK4IWH7vyO6xh8YB6Tn5A3wAAQAWABRi6emC//NN2COWEDFrCQzSo7dHywABACIAIIdrrYMvHRaAFe1BIyqeploYFdnvE8Dvh1n2S1srJ4plIQEAJVEhA7fOI6AcW0vwCmQlN836uzFbZoMyhnR471EwnQbVf4qHUa4A</pre>
 
+* Case: PSBT with unsigned tx serialized with witness serialization format
+** Bytes in Hex: <pre>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</pre>
+** Base64 String: <pre>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</pre>
+
 The following are valid PSBTs:
 
 * Case: PSBT with one P2PKH input. Outputs are empty
@@ -864,6 +868,14 @@ The following are valid PSBTs:
 ** Bytes in Hex: <pre>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</pre>
 ** Base64 String: <pre>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</pre>
 
+* Case: PSBT with global unsigned tx that has 0 inputs and 0 outputs
+** Bytes in Hex: <pre>70736274ff01000a0000000000000000000000</pre>
+** Base64 String: <pre>cHNidP8BAAoAAAAAAAAAAAAAAA==</pre>
+
+* Case: PSBT with 0 inputs
+** Bytes in Hex: <pre>70736274ff01004c020000000002d3dff505000000001976a914d0c59903c5bac2868760e90fd521a4665aa7652088ac00e1f5050000000017a9143545e6e33b832c47050f24d3eeb93c9c03948bc787b32e1300000000</pre>
+** Base64 String: <pre>cHNidP8BAEwCAAAAAALT3/UFAAAAABl2qRTQxZkDxbrChodg6Q/VIaRmWqdlIIisAOH1BQAAAAAXqRQ1RebjO4MsRwUPJNPuuTycA5SLx4ezLhMAAAAA</pre>
+
 Fails Signer checks
 
 * Case: A Witness UTXO is provided for a non-witness input