CodeId may need to preserve case, to work with case-sensitive symbol servers

[mstange]

CodeId::new() currently calls make_ascii_lowercase():

rust-debugid/src/lib.rs

Lines 297 to 302 in 9fb71ae

	/// Constructs a `CodeId` from its string representation.
	pub fn new(mut string: String) -> Self {
	string.retain(|c| c.is_ascii_hexdigit());
	string.make_ascii_lowercase();
	CodeId { inner: string }
	}

However, the casing makes a difference when looking up exe/dll files on case-sensitive symbol servers. See getsentry/symbolic#436 for background.