Store all temporary files under a single folder

[giulianopz]

Fix #2028

Any temporary file will be persisted in a new dedicated folder named as "arduino" located in the OS-specific temporary directory, e.g.:

/tmp/
├── arduino
│   ├── arduino-core-cache
│   │   └── core_arduino_avr_uno_640aa5b4d646262327bbea65c3462b39.a 
│   └── arduino-sketch-89E1544CF5F196B29E530BA6940B661F
│       ├── 06.ino.elf
│       ├── 06.ino.with_bootloader.bin
│       ├── build.options.json
│       ├── compile_commands.json
│       ├── core
│       │   ├── abi.cpp.d
[...]

This change is meant to make easier maintenance operations for both end-users and operating-systems.

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What kind of change does this PR introduce?

All code lines which reference the default tmp dir to store temporary files were changed to prefix "arduino-core-cache" and "arduino-sketch-[MD5]" dirs with "arduino/" as their parent.

What is the current behavior?

See issue #2028.

What is the new behavior?

All the temporary files will be put inside a new "arduino" folder in the default temporary directory of the OS.

Does this PR introduce a breaking change, and is titled accordingly?

Not sure if this is a braking change with respect to older versions of the cli.

[pzygielo]

Will it work in multi-user environment for the second and next users, once the first temporary arduino directory is created?

[codecov]

Codecov Report

Base: 36.43% // Head: 36.43% // No change to project coverage 👍

Coverage data is based on head (2b56131) compared to base (c0d4e44).
Patch coverage: 50.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2031   +/-   ##
=======================================
  Coverage   36.43%   36.43%           
=======================================
  Files         228      228           
  Lines       19316    19316           
=======================================
  Hits         7038     7038           
  Misses      11444    11444           
  Partials      834      834           

Flag	Coverage Δ
unit	36.43% <50.00%> (ø)

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

Impacted Files	Coverage Δ
commands/compile/compile.go	0.00% <0.00%> (ø)
arduino/sketch/sketch.go	65.53% <100.00%> (ø)
commands/lib/search.go	88.15% <0.00%> (-3.95%)	⬇️
arduino/cores/packagemanager/package_manager.go	66.58% <0.00%> (+0.75%)	⬆️

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[giulianopz]

Will it work in multi-user environment for the second and next users, once the first temporary arduino directory is created?

The second user (and next ones) will not be allowed to compile the same sketch the first user built. But only if they can access the exact same sketch folder: the name of the tmp dir of a sketch ends with an MD5 hash value generated from the path of such dir.

This happens also with the current version of the cli (doesn't it?), anyway.

This PR just deals with grouping the two main dirs containing tmp files as requested in the referenced issue. You should open a new issue, I guess, if you think that this kind of collisions can really happen (I don't know, to be honest).

[pzygielo]

This happens also with the current version of the cli (doesn't it?), anyway.

Now that you shown it I can see that arduino-core-cache locks other users already indeed.

Need internal confirmation