Shard e2e test across multiple accounts

[sobolk]

We're consistently hitting throttling in some e2e test runs. Which means that we should think about spreading the load of our e2e tests across multiple accounts.

Implementation of this task should include:

1. Building mechanism to spread traffic across multiple e2e tests accounts.
2. Building mechanism to manage e2e test accounts via CDK.
3. Add one additional e2e test account to mitigate current situation.
4. Solution should be easy to use if we need to add third account in the future.

[sobolk]

#1879

[sobolk]

Remaining work: canaries.

[sobolk]

#1902