[GUI] Poc for multi-instances

[Max-7]

Just a POC for GUI multi-instances handled using tabs.

[codecov]

Codecov Report

Merging #684 into master will decrease coverage by 39.4%.
The diff coverage is 49.74%.

@@             Coverage Diff             @@
##           master     #684       +/-   ##
===========================================
- Coverage   86.53%   47.12%   -39.41%     
===========================================
  Files         159      253       +94     
  Lines       11183    21112     +9929     
===========================================
+ Hits         9677     9950      +273     
- Misses       1506    11162     +9656

Impacted Files	Coverage Δ
parsec/core/types/__init__.py	100% <ø> (ø)	⬆️
parsec/core/gui/global_settings_widget.py	0% <ø> (ø)
parsec/core/gui/instance_widget.py	0% <0%> (ø)
parsec/core/gui/desktop.py	0% <0%> (ø)
parsec/core/gui/main_window.py	0% <0%> (ø)
parsec/core/gui/validators.py	0% <0%> (ø)
parsec/core/gui/app.py	0% <0%> (ø)
parsec/core/gui/claim_device_widget.py	0% <0%> (ø)
parsec/core/gui/register_user_dialog.py	0% <0%> (ø)
parsec/core/gui/register_device_dialog.py	0% <0%> (ø)
... and 120 more

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