Attempt to add checkout location to rebar3 path

Fix spec for download callback

Add rebar_hex_repos:remove_from_auth_config/2

- add function that allows the complete removal of an entry from auth
 config

 - add test for rebar_hex_repos:remove_from_auth_config/2

 - update test/rebar_pkg_repos_SUITE:auth_read_write_read/1 to use mocks so
 we don't append to actual hex.config files

- update bootstrap script to account for hex_core in src/vendored

Trigger rebuilds when OTP compiler version changes

Closer to what it was initially, and reduces some extra operations too.

This was a long-standing pending issue with plugins having a weird code
path handling. The work done in the previous commit to do version
detection for the compiler in dependencies along with prior PRs that
added a deps-only mode to the `compile` provider means we can now
re-introduce plugins into the 3.14 compilation mechanism.

This makes compiler version detection a compiler task concern and
removes annoying manual checks, but also solves an unreported issue
(brought up on slack only) where a plugin would no longer have its priv/
or include/ dir included when used as a checkout dependency. Essentially
the latter bug was caused by being out-of-sync with application
preparation for a build task, but by re-folding it into the main flow,
we know we have the proper support as used for deps.

Small cleanups

Rather than doing a check on each single file in a dep set (which can
grow quite large), do a dynamic rebuild of deps based on whether the DAG
mentions the files have been modified. To avoid reloading the whole DAG
more than once and then having to still map files, the compiler version
is added to rebar_compiler_erl's CritMeta for the DAG.

This comparison is only set in place to impact the
rebar_prv_install_deps call that handles pruncing and culling deps by
the compiler provider. Intra-DAG comparisons still need to be done by
rebar_compiler_erl for things to work, and the hope is that since most
built-in compiler mods end up generating erl files in deps, that will be
transparent enough to work well.

A DAG call to check the status of the dag (vsn, critmeta, existing,
etc.) has been added to do the faster check there and allowing proper
dispatch.

Plugins couldn't be updated because they don't really use the standard
dep-style facilities for things due to an early filtering.

This fix is done in three parts:

1. Add the compiler version to the data tracked in the DAG, and extract
   it from source file (when the DAG isn't around) for comparisons. Then
   on each build job, check for the compiler version as a build option
   like every other one.

   A change in compiler version represents a change in build options,
   which triggers a rebuild
2. Make it work for plugins. This requires more work because plugins
   that can find their ebin/ dir are assumed to be pre-built. Rather
   than undoing this, poke at 1 single beam file in their ebin/ dir
   and check if their compiler version matches ours to do an additional
   filter round. This is likely to be faster than reanalyzing the whole
   app, but a bit more brittle in the long run.
3. Make it work for deps. This currently is done with copy/pasted
   plugin code that needs to be reworked later if this is shown
   to be an acceptable extra step.

This patch also includes a fix on the path pruning for plugins, which
mistakenly subtracted AppInfo records from file paths; the intent was
to use the ebin dir as a comparison, which this patch fixes.

No tests have been added at this point.

closes #2391

Also Removing an unused regex macro

Add regression test for dep override infinite loop

Completes the fix presented in #2381

Uses an existing test to simply inject the regression.

Fix endless recursion in del_dep

Support pre-fetched deps for nix.

set explicit encoding when reading and writing hex config

fixes tsloughter/rebar3_hex#184

Fix compile issue on windows when language is not english

Update references to changed API elements

Reworking more of the DEBUG output to be friendly

Remove verbosity option that was taken out in relx 4.x

Fix README

Mostly changing the format of debug messages, fixing one URL that was
bad in a warning.

Since we switched to DIAGNOSTIC=1 in the crashdump, the only way to make
DEBUG=1 discoverable (outside of docs) is in the help provider.

Fixup plugin upgrade autoupdate

Didn't handle tuple-based dep definitions right

Run pkg updates on plugin upgrades

Upgrading dependencies already checked for package updates before running
the upgrade task. Plugins didn't have that mechanism in place and that
made upgrading plugins over hex trickier since users could be stuck a
long time without running an update manually.

This fix mostly readapts existing dep code to the context of plugins to
look them up one at a time and run the update as part of the upgrade.

Rework DEBUG=1 mode to be user-centric output and introduce separate DIAGNOSTIC=1 mode for implementer-level logging

This should cover most cases, including hooks.
What this specifically does is change some less useful messages for more
contextualized ones, including tying specific configurations to actions
taking place. This is particularly visible in hooks, and hopefully
provides some amount of discoverability.

Also of note:
- ebin/ directory copying is called explicitly when done since people
  have issues with that
- paths for compiled files are made relative since the analysis list
  shows the full paths already
- hooks are a bit more verbose but also more useful.