Rewrite to add support for random-acces for Crypt4GHReader

[pontus]

Unfortunately a large PR, apologies, even if I feel this is a simplification.

This PR adds opportunistic usage if the underlying data provider supports Seek, this allows for the main use case of reading small specific bits of large files. But this also allows for e.g. reading the end of a file first and then going back to an earlier position (if supported).

Interface changes are the addition of Seek and Close to permit Seeker and Closer. GetHeader has also changed from
func (c Crypt4GHReader) GetHeader() []byte to func (c *Crypt4GHReader) GetHeader() []byte.

[blankdots]

might want to bump https://github.com/neicnordic/crypt4gh/blob/master/internal/version/version.go#L10 to 1.8.0

[blankdots]

some small things.

how do you envision this being used in practice, some example code would help?

[codecov-commenter]

Codecov Report

Merging #83 (5c30913) into master (4aeb7a3) will increase coverage by 7.07%.
The diff coverage is 91.66%.

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@@            Coverage Diff             @@
##           master      #83      +/-   ##
==========================================
+ Coverage   58.47%   65.54%   +7.07%     
==========================================
  Files           6        6              
  Lines        1103     1164      +61     
==========================================
+ Hits          645      763     +118     
+ Misses        330      281      -49     
+ Partials      128      120       -8     

Flag	Coverage Δ
unittests	65.54% <91.66%> (+7.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
streaming/in.go	89.13% <91.66%> (+24.37%)	⬆️

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[pontus]

how do you envision this being used in practice, some example code would help?

Giving examples sounds like a good idea, but I'm a bit unsure where I should best do that, does someone else have opinions/suggestions?

• An examples directory in tree
• PR for the intended use case
• Out of band

?

[blankdots]

• An examples directory in tree

i vote for that, though it might be a new issue we need to create and find people to work on

[pontus]

i vote for that, though it might be a new issue we need to create and find people to work on

I can commit to creating a few small demos. Should not be a large task but it does feel like a separate PR.