Sync upstream problem-specs

[BNAndras]

I left the tests alone (see below).

checking exercises...
[warn] bob: missing 1 test case
       - multiple line question (2c7278ac-f955-4eb4-bf8f-e33eb4116a15)
[warn] forth: missing 6 test cases
       - addition -> more than two values on the stack (1e07a098-c5fa-4c66-97b2-3c81205dbc2f)
       - subtraction -> more than two values on the stack (2c8cc5ed-da97-4cb1-8b98-fa7b526644f4)
       - multiplication -> more than two values on the stack (5cd085b5-deb1-43cc-9c17-6b1c38bc9970)
       - division -> more than two values on the stack (f224f3e0-b6b6-4864-81de-9769ecefa03f)
       - combined arithmetic -> multiplication and addition (f749b540-53aa-458e-87ec-a70797eddbcb)
       - combined arithmetic -> addition and multiplication (c8e5a4c2-f9bf-4805-9a35-3c3314e4989a)
[warn] largest-series-product: missing 2 test cases
       - rejects span longer than string length (0ae1ce53-d9ba-41bb-827f-2fceb64f058b)
       - rejects empty string and nonzero span (6cf66098-a6af-4223-aab1-26aeeefc7402)
[warn] pig-latin: missing 1 test case
       - first letter and ay are moved to the end of words that start with consonants -> word beginning with consonant and vowel containing qu (e59dbbe8-ccee-4619-a8e9-ce017489bfc0)

[BNAndras]

The link checker CI is breaking on the two Computer Hope URLs from the installation directions. I think that whole manual installation section can be replaced since https://dart.dev/get-dart#install covers installing Dart several ways including the zip archive or building from source.