Extend automatic type coercion support in Delta table creation to char

[SemionPar]

Description

• extend automatic type coercion support in Iceberg table creation to char type
• generify existing test names

Additional context and related issues

https://github.com/trinodb/trino/pull/21515

Release notes

( ) This is not user-visible or docs only and no release notes are required. ( ) Release notes are required, please propose a release note for me. ( ) Release notes are required, with the following suggested text:

# Section
* Fix some things. ({issue}`issuenumber`)