handling malformed csv fields

[akshayakumar-t]

Fix CSV Panic in parse_csv VRL Function

Problem

The quick-csv library panics when parsing CSV data with a lone quote at the end of a line, causing Vector to crash when processing malformed CSV files.

Panic location: quick-csv-0.1.6/src/columns.rs:25:44

Root Cause

In quick-csv, when iterating columns via bytes_columns(), the code attempts to strip quotes from quoted fields:

if s.starts_with(&[b'\"']) { &s[1..s.len() - 1] } else { s }

Input	Description
a,"	Field followed by lone quote
"	Entire line is just a quote
,"	Empty field then lone quote

Changes
src/stdlib/parse_csv.rs: Added ends_with_lone_quote() function and validation check before CSV parsing
Tests Added
lone_quote_at_end - a,"
just_a_quote - "
empty_field_then_lone_quote - ,"