Re-evaluate case-sensitivity of identifiers (both delimited and un-delimited)

[alancai98]

Based on the recent discussions related to case-sensitivity of PartiQL identifiers, we should evaluate the correctness of delimited and un-delimited identifiers to each of the targets.

More on the identifiers in each target:

• Redshift https://docs.aws.amazon.com/redshift/latest/dg/r_names.html
• Spark 3.1.1 https://spark.apache.org/docs/3.1.1/sql-ref-identifier.html
• Trino https://trino.io/docs/current/language/reserved.html#language-identifiers

The different SQL dialects also support different configuration settings related to case-sensitivity of identifiers.