Avoid creating extra `relation` and `build_arel` in `_create_record` and `_update_record` (#29999)

Currently `_create_record` and `_update_record` in `Persistence` are
creating extra `unscoped` and calling `build_arel` in the relation. But
`compile_insert` and `compile_update` can be done without those
expensive operation for `SelectManager` creation. So I moved the
implementation to `Persistence` to avoid creating extra relation and
refactored to avoid calling `build_arel`.

https://gist.github.com/kamipo/8ed73d760112cfa5f6263c9413633419

Before:

```
Warming up --------------------------------------
      _update_record   150.000  i/100ms
Calculating -------------------------------------
      _update_record      1.548k (±12.3%) i/s -      7.650k in   5.042603s
```

After:

```
Warming up --------------------------------------
      _update_record   201.000  i/100ms
Calculating -------------------------------------
      _update_record      2.002k (±12.8%) i/s -      9.849k in   5.027681s
```

30% faster for STI classes.

0 files changed, 0 insertions, 0 deletions