Leverage Cow<'val, str> in scanner::Content

[almann]

In #15, we added some new tokens that manipulate the text to be put into the content. We should leverage the borrowed form of the Cow when possible. There are at least three places where we should return the borrowed variant when there is no replacement:

partiql-lang-rust/partiql-parser/src/scanner.rs

Lines 151 to 155 in d309746

	/// Removes PartiQL escapes from a string literal and dequotes it.
	#[inline]
	fn normalize_string_lit(raw_text: &str) -> Cow<str> {
	raw_text[1..(raw_text.len() - 1)].replace("''", "'").into()
	}

partiql-lang-rust/partiql-parser/src/scanner.rs

Lines 157 to 163 in d309746

	/// Removes PartiQL escapes from a quoted identifier and dequotes it.
	#[inline]
	fn normalize_quoted_ident(raw_text: &str) -> Cow<str> {
	raw_text[1..(raw_text.len() - 1)]
	.replace(r#""""#, r#"""#)
	.into()
	}

partiql-lang-rust/partiql-parser/src/scanner.rs

Line 189 in d309746

Rule::Keyword => Content::Keyword(text.to_uppercase().into()),

[almann]

As per @zslayton's original note in #15:

Not sure it's worth the dependency, but there's a small crate called cow-utils that provides cow_replace, cow_to_uppercase etc.

I am not sure it is worth the dependency as well, but something to definitely consider.