Bundle rework

[rm-dr]

Our current bundle scheme is causing quite a few bugs. This PR (paired with tectonic-typesetting/tectonic-texlive-bundles#14) resolves many of these by implementing proper search paths in bundles.

These changes are not be breaking. Old zip and bundles will work with this PR.
(I have, however, removed the scripts that create them. They should eventually be deprecated.)

Changes in this PR:

• A new bundle format (see Huge rewrite, many fixes tectonic-texlive-bundles#14)
• File search paths (also documented in the bundle repo)
• Bundle autodetection from url (thus, --web-bundle has been removed, and --bundle now handles both URLs and paths)
• Bundle caching rework (mostly invisible to the user, enables cleaner code)
• Cache organization rework (the bundle cache needs fewer files and is in its own subdir)
• Many minor bundle-related cleanups and optimizations

Most changes in this PR are in the bundles crate. Changes in other files are usually minor side-effects thanks to a slightly different API.

[vlasakm]

Just some things I noticed at firts glance.

[pkgw]

Thanks for all this work! As I remarked in the texlive-bundles PR, I wasn't getting any notifications about your work on this topic. I hope to start reading over your PRs and understanding what you've been working on, although to be honest it will likely take me a lot longer to do so than I'd like.

[rm-dr]

Alright, that should be it. The new cache is multi-process-safe via renames, tests pass, and clippy errors have been fixed.
Both this and tectonic-typesetting/tectonic-texlive-bundles#14 should be ready to merge.

[codecov]

Codecov Report

Attention: Patch coverage is 38.40000% with 462 lines in your changes missing coverage. Please review.

Project coverage is 46.11%. Comparing base (b3b66f2) to head (4d3f8b6).
Report is 47 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/bundles/src/ttb.rs	0.00%	136 Missing ⚠️
crates/bundles/src/ttb_net.rs	0.00%	108 Missing ⚠️
crates/bundles/src/ttb_fs.rs	0.00%	62 Missing ⚠️
crates/bundles/src/itar.rs	72.09%	36 Missing ⚠️
crates/bundles/src/cache.rs	77.69%	29 Missing ⚠️
crates/bundles/src/lib.rs	59.42%	28 Missing ⚠️
crates/bundles/src/dir.rs	0.00%	18 Missing ⚠️
crates/bundles/src/zip.rs	0.00%	18 Missing ⚠️
crates/io_base/src/app_dirs.rs	54.54%	5 Missing ⚠️
src/docmodel.rs	63.63%	4 Missing ⚠️
... and 12 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1121      +/-   ##
==========================================
- Coverage   46.40%   46.11%   -0.30%     
==========================================
  Files         176      179       +3     
  Lines       65118    65413     +295     
==========================================
- Hits        30221    30168      -53     
- Misses      34897    35245     +348     

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[pkgw]

CC @CraftSpider here too.

[rm-dr]

Hmmm
A few tests are still failing on azure, not sure why.
Everything passes on my machine.

[pkgw]

Hmm, I'm not sure why this error would only be showing up in the cross-tests. The one thing that I can think of is that those run through the cross program, which filters the environment variables that propagate down to the subprograms that it runs ... but I don't see anything about this particular error that would depend on environment variables being set.

[rm-dr]

Just fixed #74. File names with spaces are now safe in ttbv1 bundles---but newlines will still cause errors.

I'm not sure that's a problem, though, since I've never seen a legitimate use case for files with newlines.

[rm-dr]

Here's an idea: should this new bundle format also include latex format files?

Now that the bundle-building code is in Rust, it shouldn't be too hard to generate format files while we build the bundle. (assuming format files are identical on all machines)

Would be nice to do that here, so that we only have one round of big, possibly disruptive changes.