* tidy up godoc

* move data availability config decision to channel submission time

instead of channel creation time

Also, cache the ChannelConfig whenever we switch DA type so it is used by default for new channels

* fix test

* formatting changes

* respond to PR comments

* add unit test for Requeue method

* reduce number of txs in test block

* improve test (more blocks in queue)

* hoist pending tx management up

* wip

* tidy up test

* wip

* fix

* refactor to do requeue before calling nextTxData

* introduce ErrInsufficientData

do not return nextTxData from channel which was discarded by requeue

* run test until nonzero data is returned by TxData

* break up and improve error logic

* fix test to anticipate ErrInsufficientData

* after requeuing, call nextTxData again

* remove unecessary checks

* move err declaration to top of file

* add some comments and whitespace

* hoist lock back up to TxData

* rename variable to blocksToRequeue

* remove panic

* add comment

* use deterministic rng and nonecompressor in test

* test: increase block size to fill channel more quickly

* remove ErrInsufficientData

replace with io.EOF as before

* tidy up

* typo