[sei] Governance proposal for new token pair on the dex

[Kbhat1]

https://linear.app/passportlabs/issue/PAS-812/[sei]-require-governance-proposal-for-new-token-pair-on-the-dex

• removes ability to submit transaction to create a dex whitelisted token pairs
• Adds governance proposal type to add dex whirelisted token pairs
• Does not add ability to arbitrarily add any denom - only restricted to current enum set

Sample Register Pair proposal.json

{
  "title": "Add usdc,sei + usdc,atom pair to contract 1 and usdc,btc pair to contract 2",
  "description": "gov proposal to update contract 1 and contract 2 registered pairs",
  "batch_contract_pair": [
    {
      "contract_addr":  "contract_1_address",
      "pairs": [
        {
          "price_denom": "usdc",
          "asset_denom": "sei"
        },
        {
          "price_denom": "usdc",
          "asset_denom": "atom"
        }
      ],
    },
    {
      "contract_addr": "contract_2_address",
      "pairs": [
        {
          "price_denom": "usdc",
          "asset_denom": "btc"
        }
      ],
    },
  ],
  "deposit": "10000000usei"
}

[codchen]

maybe add an example proposal json file somewhere? either under x/dex/examples or part of this PR description is fine