Introduce PAX header support

[piurafunk]

In my use case, I'm pulling very large files from a docker volume, using the Docker HTTP API endpoint. Because the files I'm pulling are larger than 8 GiB, the Docker engine prefixes the data stream with a PAX header docs. They do this to indicate the size of the file is larger than 8 GiB (tar format has a limitation the makes it so it can only record the size of the file as 8 GiB).

This PR should introduce support for the size parameter in a PAX header. There are other headers that can be implemented, but I wanted to get this feature in, because it's the core of how the header can be processed. As other use cases come up, they can be added.

The test added takes quite a long time to run. It tests a tar archive that contains 1 x 10 GiB file, 2 x 10 GiB files, and 3 x 10 GiB files, to ensure it would work on a directory of very large files. Currently the test is configured to run if the CI env var is set, which GitHub Actions has set on their workflows (docs). For local development, they will be marked as skipped, but a local env var of TEST_MASSIVE_FILE=true would allow it to run as well. This way we know the tests pass before merging a PR, but development of features unrelated to these large files is faster to iterate on. If this should be changed so that CI runs are faster, I am happy to do so.

[jakubboucek]

This PR looks very interesting for me. Thanks! 👍 I never heard about PAX extension.

I want to merge it, but i want to fully understand all properties of that and knows all consequecies to code quality and stability.

Please be patient.

[piurafunk]

9de2244 and 27fcf44 were to fix a PHPStan error:

 ------ ------------------------------------------------------------------------
  Line   StreamReader.php
 ------ ------------------------------------------------------------------------
  175    Parameter #2 $length of function fread expects int<1, max>, int given.
 ------ ------------------------------------------------------------------------

By introducing checks for 0 length tar archives, it breaks legitimate tar archives that have 0 length, such as directories. I'm fine rolling those commits back, and instead instructing PHPStan to ignore that specific error on that line with // @phpstan-ignore argument.type. Does that work for you?

[piurafunk]

I went ahead and applied that PHPStan ignore comment. I also fixed another bug I found, related to null byte padding.

[jakubboucek]

Thanks. I am still very busy, and I expect a delay of a few months before I can review and merge. Sorry about that.