## Problem
We use a pretty old version of `mypy` 1.3 (released 1.5 years ago), it
produces false positives for `typing.Self`.
## Summary of changes
- Bump `mypy` from 1.3 to 1.13
- Fix new warnings and errors
- Use `typing.Self` whenever we `return self`
## Problem
On Debian 12 (Bookworm), Python 3.11 is the latest available version.
## Summary of changes
- Update Python to 3.11 in build-tools
- Fix ruff check / format
- Fix mypy
- Use `StrEnum` instead of pair `str`, `Enum`
- Update docs
The metrics include a histogram of how long we need to wait for a
GetPage request, number of reconnects, and number of requests among
other things.
The metrics are not yet exported anywhere, but you can query them
manually.
Note: This does *not* bump the default version of the 'neon' extension. We
will do that later, as a separate PR. The reason is that this allows us to roll back
the compute image smoothly, if necessary. Once the image that includes the
new extension .so file with the new functions has been rolled out, and we're
confident that we don't need to roll back the image anymore, we can change
default extension version and actually start using the new functions and views.
This is what the view looks like:
```
postgres=# select * from neon_perf_counters ;
metric | bucket_le | value
---------------------------------------+-----------+----------
getpage_wait_seconds_count | | 300
getpage_wait_seconds_sum | | 0.048506
getpage_wait_seconds_bucket | 2e-05 | 0
getpage_wait_seconds_bucket | 3e-05 | 0
getpage_wait_seconds_bucket | 6e-05 | 71
getpage_wait_seconds_bucket | 0.0001 | 124
getpage_wait_seconds_bucket | 0.0002 | 248
getpage_wait_seconds_bucket | 0.0003 | 279
getpage_wait_seconds_bucket | 0.0006 | 297
getpage_wait_seconds_bucket | 0.001 | 298
getpage_wait_seconds_bucket | 0.002 | 298
getpage_wait_seconds_bucket | 0.003 | 298
getpage_wait_seconds_bucket | 0.006 | 300
getpage_wait_seconds_bucket | 0.01 | 300
getpage_wait_seconds_bucket | 0.02 | 300
getpage_wait_seconds_bucket | 0.03 | 300
getpage_wait_seconds_bucket | 0.06 | 300
getpage_wait_seconds_bucket | 0.1 | 300
getpage_wait_seconds_bucket | 0.2 | 300
getpage_wait_seconds_bucket | 0.3 | 300
getpage_wait_seconds_bucket | 0.6 | 300
getpage_wait_seconds_bucket | 1 | 300
getpage_wait_seconds_bucket | 2 | 300
getpage_wait_seconds_bucket | 3 | 300
getpage_wait_seconds_bucket | 6 | 300
getpage_wait_seconds_bucket | 10 | 300
getpage_wait_seconds_bucket | 20 | 300
getpage_wait_seconds_bucket | 30 | 300
getpage_wait_seconds_bucket | 60 | 300
getpage_wait_seconds_bucket | 100 | 300
getpage_wait_seconds_bucket | Infinity | 300
getpage_prefetch_requests_total | | 69
getpage_sync_requests_total | | 231
getpage_prefetch_misses_total | | 0
getpage_prefetch_discards_total | | 0
pageserver_requests_sent_total | | 323
pageserver_requests_disconnects_total | | 0
pageserver_send_flushes_total | | 323
file_cache_hits_total | | 0
(39 rows)
```
