Fix/Move toString into utils.

[lhruby]

Description

Move toString into utils. This solves the issue that modules like serdes::protobuf would depend on types, which in turn creates cyclic dependencies.

A move to fmt::format_as is not included and will be implemented in a follow up.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• If this is a new component I have added examples.
• I updated the README and related documentation.