util: rename bnToRlp to bnToUnpaddedBuffer

[ryanio]

This PR renames bnToRlp to bnToUnpaddedBuffer to better describe its function (closes ethereumjs/ethereumjs-util#284)

It also converts some uses of unpadBuffer(toBuffer(bn)) to the function, and adds a test for it in the util package. bnToRlp is kept as a deprecated alias that can be removed in a future major version.

[codecov]

Codecov Report

Merging #1293 (f9831c8) into master (26de933) will increase coverage by 1.95%.
The diff coverage is 100.00%.

Flag	Coverage Δ
block	86.44% <100.00%> (+0.24%)	⬆️
blockchain	84.36% <ø> (-0.07%)	⬇️
client	84.48% <ø> (ø)
common	88.25% <ø> (-0.46%)	⬇️
devp2p	83.82% <ø> (ø)
ethash	82.83% <ø> (ø)
tx	89.61% <100.00%> (+0.11%)	⬆️
vm	87.06% <ø> (+5.70%)	⬆️

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[holgerd77]

Thanks, nice, yes this is actually a lot more readable. 😄

Please always use @deprectated for the code docs on such deprecations, otherwise e.g. Visual Studio is not picking this up by striking through. Have added on a review-commit.

Unrelated to PR: I think these two/three methods bnToHex(), bnToUnpaddedBuffer() (and bnToRlp()) are very much misplaced in the types module and should rather go to bytes. Have added to the v6 notes (let me know if you disagree).

[ryanio]

@holgerd77 sounds good, ah thanks for the @deprecated tag I forgot to add that.

I think we can go ahead and move those methods to the bytes file as a "tiny fixes" issue rather than breaking change, since they are exported the same on the top level ethereumjs-util module (i.e. import { bnToHex } from 'ethereumjs-util') so it wouldn't be breaking unless someone was importing from the file directly, but we don't suggest or encourage that anywhere.

[holgerd77]

@ryanio hmm, I would prefer to rather be cautious here and only do on next breaking release, also absolutely no urgency here. In the README these modules are stated very explicitly and it is as valid to import from the respective modules (can be even seen as a bit more clean) than from the top level. So I guess this can't really be foreseen if people are doing this or not.