convert: Minor cleanup

This commit implements some minor cleanup of various converter- and
convert test-related code:

* Improves the log messages regarding which converter was returned for a
request.

* Modifies the result checking code in the converter tests to only
report an out-of-range sample error once, rather than reporting every
out-of-range sample encountered during the test. This vastly cuts down
on the output when a conversion has failed.

* Adds a function `reverse_converter()` which, given a
`convert::id_type` describing a conversion from C1 to C2, returns a
`convert::id_type` describing the reverse conversion (C2 to C1).

* Removes two redundant test cases from the converter test.

0 files changed, 0 insertions, 0 deletions