Add a golden test of update-committee

[smelc]

As #344 shows, we have no tests of update-committee (the PR did not need to adapt any test!). This issue keeps track of adding one, using @CarlosLopezDeLara's input (below).

cardano-cli conway governance action update-committee \
--testnet \
--governance-action-deposit 0 \
--stake-verification-key-file example/utxo-keys/stake1.vkey \
--proposal-url https://shorturl.at/asIJ6 \
--proposal-file example/transactions/cc_proposal.txt \
--add-cc-cold-verification-key-file example/cc/cold1-cc.vkey \
--epoch 202 \
--add-cc-cold-verification-key-file example/cc/cold2-cc.vkey \
--epoch 252 \
--quorum 51/100 \
--out-file example/transactions/update-committee.action

cat example/transactions/new-committee.action
{
    "type": "Governance proposal",
    "description": "",
    "cborHex": "8400581de05fd2fa72549639d76d48569eec31e63a5692e58375b2c708f27b299a8504f680a28200581c03fb852259ba0feb3f71ec2f5a108c133599d6a652aaed03590bcce318fc8200581cf7f2a37830d35650a6132f6bb9752e1967c158e842e3bbd5ac7b2a4818cad81e821833186482781968747470733a2f2f73686f727475726c2e61742f6173494a3658203d2a9d15382c14f5ca260a2f5bfb645fe148bfe10c1d0e1d305b7b1393e2bd97"
}

[0, h'E05FD2FA72549639D76D48569EEC31E63A5692E58375B2C708F27B299A', [4, null, [], {[0, h'03FB852259BA0FEB3F71EC2F5A108C133599D6A652AAED03590BCCE3']: 252, [0, h'F7F2A37830D35650A6132F6BB9752E1967C158E842E3BBD5AC7B2A48']: 202}, 30([51, 100])], ["https://shorturl.at/asIJ6", h'3D2A9D15382C14F5CA260A2F5BFB645FE148BFE10C1D0E1D305B7B1393E2BD97']]

Originally posted by @CarlosLopezDeLara in #344 (comment)

[smelc]

My personal notes for generating the input files for this test:

> cabal run cardano-cli -- stake-address key-gen --verification-key-file stake1.vkey --signing-key-file stake2.skey
> cabal run cardano-cli -- conway governance committee key-gen-cold --cold-verification-key-file cold1-cc.vkey --cold-signing-key-file /dev/null
> cabal run cardano-cli -- conway governance committee key-gen-cold --cold-verification-key-file cold2-cc.vkey --cold-signing-key-file /dev/null
>  cat cc_proposal.txt 
WE, THE PEOPLE of Barataria, in order to maintain peace and harmony among us, establish this Constitution for our 
precious Insula of Barataria:

Article 1. The person who waters wine or changes the label should lose his life for it.