Currently, `REGEX_DATETIME_DIFF` doesn't match for all occurrences of
`DATETIME_DIFF` and `postgres-make-concepts.sql` errors out. For example:

```
psql:demographics/age.sql:30: ERROR:  column "year" does not exist
LINE 22: ...mittime, DATETIME(pa.anchor_year, 1, 1, 0, 0, 0), YEAR) + pa..
```

Also, `PERL_REGEX_ROUND` doesn't correctly match `ROUND(...)` with
nested functions, for example with a nested `DATETIME_DIFF`:

```
psql:demographics/icustay_detail.sql:33: ERROR:  syntax error at or near "as"
LINE 17: , ROUND( CAST( DATETIME_DIFF(ie.outtime as numeric),ie.intim...
```

Update both regular expressions accordingly.

Since 8ed4060 the relation name prefix
is `mimiciv_`.

The following auto generated files for PostgreSQL were not added to the
repo yet:

postgres/medication/milrinone.sql
postgres/medication/norepinephrine_equivalent_dose.sql
postgres/medication/vasoactive_agent.sql

Some concepts have a dependency on others, for example
`norepinephrine_equivalent_dose.sql` expects
`mimiciv_derived.vasoactive_agent` to exist.

Fixup for 43a4245