pkg/workflows/sdk: add WorkflowSpecFactory.BeginSerial/BeginAsync

[jmank88]

Depends on #790

This PR extends WorkflowSpecFactory to include BeginSerial() and BeginAsync() methods for toggling between two builder modes.

Here is an example from a test which reads from two APIs and one chain, then writes on chain:

flowchart
	
	trigger-chain-event[\"<b>trigger-chain-event</b><br>trigger<br><i>(chain_reader[at]1.0.0)</i>"/]
	
	compute-bar["<b>compute-bar</b><br>action<br><i>(custom_compute[at]1.0.0)</i>"]
	get-bar --> compute-bar
				
	compute-foo["<b>compute-foo</b><br>action<br><i>(custom_compute[at]1.0.0)</i>"]
	get-foo --> compute-foo
				
	get-bar["<b>get-bar</b><br>action<br><i>(http[at]1.0.0)</i>"]
	trigger-chain-event --> get-bar
				
	get-foo["<b>get-foo</b><br>action<br><i>(http[at]1.0.0)</i>"]
	trigger-chain-event --> get-foo
				
	read-token-price["<b>read-token-price</b><br>action<br><i>(chain_reader[at]1.0.0)</i>"]
	trigger-chain-event --> read-token-price
				
	data-feeds-report[["<b>data-feeds-report</b><br>consensus<br><i>(offchain_reporting[at]1.0.0)</i>"]]
	compute-bar -- Value --> data-feeds-report 
				compute-foo -- Value --> data-feeds-report 
				read-token-price -- Value --> data-feeds-report 
				
	unnamed7[/"target<br><i>(write_ethereum-testnet-sepolia[at]1.0.0)</i>"\]
	data-feeds-report --> unnamed7
				

Here is the same workflow with (dotted) edges added in order to serialize the overall DAG:

flowchart

    trigger-chain-event[\"<b>trigger-chain-event</b><br>trigger<br><i>(chain_reader[at]1.0.0)</i>"/]

    compute-bar["<b>compute-bar</b><br>action<br><i>(custom_compute[at]1.0.0)</i>"]
    get-bar --> compute-bar

    compute-foo["<b>compute-foo</b><br>action<br><i>(custom_compute[at]1.0.0)</i>"]
    get-foo --> compute-foo

    get-bar["<b>get-bar</b><br>action<br><i>(http[at]1.0.0)</i>"]
    trigger-chain-event --> get-bar

    get-foo["<b>get-foo</b><br>action<br><i>(http[at]1.0.0)</i>"]
    trigger-chain-event --> get-foo

    read-token-price["<b>read-token-price</b><br>action<br><i>(chain_reader[at]1.0.0)</i>"]
    trigger-chain-event --> read-token-price

    data-feeds-report[["<b>data-feeds-report</b><br>consensus<br><i>(offchain_reporting[at]1.0.0)</i>"]]
    compute-bar -- Value --> data-feeds-report
    compute-foo -- Value --> data-feeds-report
    read-token-price -- Value --> data-feeds-report

    unnamed7[/"target<br><i>(write_ethereum-testnet-sepolia[at]1.0.0)</i>"\]
    data-feeds-report --> unnamed7

    compute-foo -..-> get-bar
    compute-bar -..-> read-token-price

TODO

• [ ] make Condition functional