Allow quotes in `#:` file-level directives

[jjonescz]

For example:

#:project "../lib"
#:package "Humanizer"@2.0
#:property Xyz = "abc "

We should preserve leading and trailing whitespace inside the quoted string.
Escaped values like \" should be supported per C# rules (we should use Roslyn lexer if possible).

• Discussed previously at Each app directive (#:) kind should allow only one separator #48841
• #r requires quotes and we will support #r as well, see Add support for #r "nuget: xxx" to run-file for ease of code transfer from csx #49199