Switch utc_to_timestamp to .timestamp() where possible (#109729)
* Switch utc_to_timestamp to .timestamp()
.timestamp() is faster now in newer cpython
```
from homeassistant.util.dt import utc_to_timestamp, utcnow
import timeit
now = utcnow()
print(timeit.timeit('utc_to_timestamp(now)',globals={"now":now,"utc_to_timestamp":utc_to_timestamp}))
print(timeit.timeit('now.timestamp()',globals={"now":now}))
```
utc_to_timestamp = 0.18721245788037777
timestamp = 0.11421508435159922
* compat
* revert
* revert
* revert
* revert
* revert
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