ibc: Chain ID parsing incorrectly accepts newlines

[avahowell]

Describe the bug
When parsing chain IDs, ibc-types uses a more lenient regex than ibc-go's regex.

For example, ibc-go will consider the chain ID \n-foo-1 to have revision number 0, whereas penumbra-ibc will consider it to have revision number 1.

This likely does not have any security impact, but it is a deviation from the specification and can potentially lead to an issue in the future.

Expected behavior
Include a newline (and possibly anchors) in ibc-types's version of the regex.

pub fn is_epoch_format(chain_id: &str) -> bool {
  - let re = safe_regex::regex!(br".*[^-]-[1-9][0-9]*");
  + let re = safe_regex::regex!(br"^.*[^\n-]-[1-9][0-9]*$");
       re.is_match(chain_id.as_bytes())
   }