fix: Disable table name normalisation as default behaviour

[milenkovicm]

Which issue does this PR close?

• Closes Inconsistent datafusion.sql_parser.enable_ident_normalization=false behaviour #18675.

Rationale for this change

There are cases for which case sensitive column names and table references are needed, so having forced to_ascii_lowercase for names breaks support for them.

datafusion.sql_parser.enable_ident_normalization=false will help with column names but table names and few other things will be converted to lowercase, or not (as described in the bug)

This is potentially VERY BREAKING change, it disables forced to_ascii_lowercase for table reference and columns, as behaviour was hardcoded.

What changes are included in this PR?

• disable forced to lowercase conversion for table ref and columns
• test to verify bug

Are these changes tested?

yes

Are there any user-facing changes?

yes, some users can be affected if they have enable_ident_normalization disabled or if they rely on datafusion to automatically do ident_normalization