Split up GitHubActionsRoleNextstrainBatchJobs role to avoid quota limit on trust policy

[joverlee521]

Follow up to @tsibley 's comment

While we'll eventually need to split that GitHubActionsRoleNextstrainBatchJobs role into two (or otherwise tweak it) to accommodate the role trust policy length limit, in the meantime I've bumped that quota from 2,048 chars to 4,096 chars (the max that's automatically approved).

Each pathogen repo adds ~110 characters, so we'll hit the new limit after adding another ~18 pathogens.