Improve tournament pool logic to require switching less

[Sendouc]

• Pools have limit of 100 members in it after which they become unreliable
• Current logic (inside Tournament class resolvePoolCode) has support for

1. pool by group
2. pool by bracket number
3. pool by hosting team

We could make some further optimizations to reduce the amount of time people need to change pool during tournament name for small tournaments (and/or small brackets) say less than 48 teams (subject for optimizations) just use one pool for the whole tournament. So maybe something like:

1. if tournament has less than X teams, use common pool
2. if tournament has more than X teams but bracket has less than X teams, use common pool for the bracket
3. Otherwise use current behavior