Feat: Use SpokePoolManager instead of SpokePoolClients

[dijanin-brat]

Use SpokePoolManager instead of SpokePoolClients object to enforce devs to handle wrong/incorrect chainIds.

[nicholaspai]

How does this improve current code, I'm not quite following?

[dijanin-brat]

How does this improve current code, I'm not quite following?

@nicholaspai Idea is to change every place where we are using spokePoolClients object directly with SpokePoolManager. Because, if we access the object directly like spokePoolClients[chainId], and there is no value for that specific key (chainId), it will return undefined but typescript will not enforce devs to handle that case. This is the first iteration of changes (it should be added on more places later) so we always handle cases where it can return undefined (so we can decide, in code, how to handle those cases and not have unexpected runtime errors). Does that make sense?

[james-a-morris]

OOC why are we removing the protected + readonly?

[dijanin-brat]

spokePoolClients will not be class property anymore. It is replaced with SpokePoolManager and we will use spokePoolClients just as an argument for SpokePoolManager initialization.