Add check for "dotlines" with cabal 3.0+

[tbidne]

Adds a cabal check for #11518.

Click to expand outdated explanation

Adds a warning for #11518. I'm not too familiar with this part of the codebase, but the changes seem straightforward.

Essentially wraps

fromUTF8BS :: ByteString -> String

with

parseLine3 :: Position -> BS.ByteString -> ParseResult src String

which adds a warning if the string matches the same dot check pre-3.0 (trim bs == "."). The rest is just mechanical changes to accommodate the ParseResult.~~

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[tbidne]

Not really sure what the lone failure is about. It's Backpack\T5634 with the lib-suite test:

*** unexpected failure for PackageTests\Backpack\T5634\setup.test.hs

ci log

I'm not seeing any obvious reasons, like network errors or output mismatch. 🤷

[geekosaur]

It's a sporadic failure with ghc 9.2.8 on Windows: ghc-pkg exits with failure but no messages. It'll happen for a while (up to a couple hours) and then start working again.

[tbidne]

Embarrassing oversight: I just realized the original PR added the check to cabal build, not cabal check. I rectified this, so it's now on check (the test verifies that build is unaffected).

Right now it's a separate commit so the difference is easier to see, but I intend to squash them into one commit once I get confirmation that check is what we want.

Apologies for the churn!

Edit: Went ahead with the squash. The diff against the prior commit can be seen here.