Upgrade framework on Meter Mainnet

[guidiaz]

And deploy new pfs:

• BTC/USD, ETH/USD, USDC/USD, USDT/USD, MTRG/USD

[guidiaz]

Related PRs:

• https://github.com/witnet/witnet-solidity-bridge/pull/395
• https://github.com/witnet/witnet-feeds/pull/25
• https://github.com/witnet/witnet-price-feeds/pull/333
• https://github.com/otherplane/bridge-iac/pull/137

[guidiaz]

Added pfs to https://docs.witnet.io