Add Conditional Order factory

[anxolin]

This PR prepares the polling to hook it up to https://github.com/cowprotocol/tenderly-watch-tower

Conditional Order Factory

The main addition in this PR is this factory.

The factory responsibility is to create Conditional Orders from the ConditionalOrderParams (handler, salt, staticInput)

It has some config with the factory methods per handler.

Some basic usage is:

# Create factory
const factory = new ConditionalOrderFactory({
  // Register of all known order types
  [TWAP_ADDRESS]: (params) => Twap.fromParams(params),
})

# Then you can create an order just by 
const conditionalOrder = fromParams.fromParams({
   handler,
   salt
   staticInput
})

# Default Registry
The factory requires a registry in order to work
The registry has the different factory methods per handler

The SDK will also export some default config with all the handlers/facttory it knows: for now, only `Twap`: https://github.com/cowprotocol/cow-sdk/pull/151/files#diff-cc93eafdc1844adfa999909a952edcc111abb3031a0eac57403966f6a3c8d00eR5

# Use the order
console.log('Order: ', conditionalOrder.id)

# Now is easy to do polling (and custom validation), without even knowing what order we are processing
console.log('Polling result: ', await order.poll(owner, chainId, provider ))

Companion PR

This PR will have a companion PR in tenderly watch tower project:
cowprotocol/watch-tower#16

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[coveralls]

coverage: 76.271% (-1.3%) from 77.586% when pulling 32e7421 on conditional-order-factory into e77585b on main.

[mfw78]

Looks good, please see nits in the review here yet to be included (typos etc).