Reduce orm overhead by grouping object expiration

[bdraco]

Proposed change

While #40982 solved the performance overhead of expiring every time
we commit the event session, it caused a regression which was
fixed in #41349.

Ideally we could avoid the overhead of expiring objects on commit
since we are never going to use them again by using expunge after
the commit to remove the objects we no longer need. Unfortunately
this causes sqlalchemy to spend quite a bit of time sorting out
state when adding new objects to the event session after an
expunge_all so it wasn't a viable option.

As not expring the objects causes unexpected side effects, we can
limit the impact of having to expring them by only doing the expire
every 120 commits (by default every 2 minutes) instead of every commit
(by default every second). This works because the expire operation
itself is expensive reguardless of the number of objects it is expiring.

To verify this approach does not leak memory, a scale test integration
was created (https://github.com/bdraco/scaletest) and run for hours
along with an objgraph dump setup every 30 seconds to verify States
and Events were being properly disposed of
(https://mg.pov.lt/objgraph/objgraph.html#locating-and-filtering-objects)

In testing this took a machine running the scaletest integration
from 100% cpu to 4% cpu

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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