[fuzz] Only set HUF_repeat_valid if loaded table has all non-zero weights (#1898)

Fixes a fuzz issue where dictionary_round_trip failed because the compressor was generating corrupt files thanks to zero weights in the table.

* Only setting loaded dict huf table to valid on non-zero

* Adding hasNoZeroWeights test to fse tables

* Forbiding nbBits != 0 when weight == 0

* Reverting the last commit

* Setting table log to 0 when weight == 0

* Small (invalid) zero weight dict test

* Small (valid) zero weight dict test

* Initializing repeatMode vars to check before zero check

* Removing FSE changes to seperate pr

* Reverting accidentally changed file

* Negating bool, using unsigned, optimization nit