When tokenizing markup (e.g. HTML) element attributes
can have quoted or unquoted values (e.g. `a=b` or `a="b"`).
The `ATTR_VALUE` tokens were capturing the quotes, which
was inconsistent and also affected source-mapping.
Now the tokenizer captures additional `ATTR_QUOTE` tokens,
which the HTML related parsers understand and factor into their
token parsing.
PR Close#28055