scalar-field format rejects datetime.interval type

Bug description

Version: Tarantool 3.7.0-entrypoint-55-ga755e0ed38

Actual behavior

1. datetime as scalar is accepted, but interval as scalar is rejected

dt = require('datetime')

s = box.schema.space.create('s', {format = {{'id', 'unsigned'}, {'d', 'scalar'}}, temporary = true})
---
...

s:create_index('ii')
...

s:insert({1, dt.new()})
---
- [1, '1970-01-01T00:00:00Z']
...

s:insert({2, dt.interval.new()})
---
- error: 'Tuple field 2 (d) type does not match one required by operation: expected
    scalar, got extension'
...

2. datetime and interval is missed in the docu in enumerations of scalar and any types: https://www.tarantool.io/en/doc/latest/platform/ddl_dml/value_store/#scalar

3. It seems box.schema.space.create() and similar format tests missed datetime and interval types.

Expected behavior

1. interval type must be accepted as scalar.

2. docu fixed.

Start by reproducing the scalar format behavior with box.schema.space.create() and the datetime interval example from the report, then inspect the related format tests. Confirm that interval is accepted as scalar, add coverage for datetime and interval where the report says tests are missing, and update the scalar and any documentation page to list both types.