fix: improve escaping of identifiers

[agavra]

Description

As part of the work around quoted identifiers, we need to be able to properly escape not just reserved words - but anything that doesn't parse as a proper identifier. I accomplished this by using the identifier rule to parse an identifier instead of trying to hack our own rules by creating the set of reserved words.

The new code is all in IdentifierUtil and I removed the old code in ParserUtil.

Testing done

• unit testing
• end to end tests after my implementation of quoted identifiers prototype

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[spena]

I like this, so we don't have to add reserved words in a Set.
LGTM