Upgrade syntax to 3.10

[hippalectryon-0]

This is a "long" PR diff-wise, but the content is very simple (and reproducible, if anyone wants to double-check I didn't add any weird code):

Step 1

• Run find qubesadmin -name '*.py' -exec uvx -p 3.10 pyupgrade --py310-plus {} +

Step 2

• Manually review every change.
• Make some very small adjustments (there were three at most, extremely minor - you can view them by diffing 2eb6fef against the output of the command above)

Step 3

• Run pylint and correct errors (a132ad6)

[codecov]

Codecov Report

❌ Patch coverage is 64.66165% with 47 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.04%. Comparing base (8ebd096) to head (498ac1a).

Files with missing lines	Patch %	Lines
qubesadmin/backup/restore.py	30.00%	7 Missing ⚠️
qubesadmin/tools/__init__.py	44.44%	5 Missing ⚠️
qubesadmin/tools/dochelpers.py	0.00%	5 Missing ⚠️
qubesadmin/tools/qvm_backup.py	0.00%	4 Missing ⚠️
qubesadmin/tools/qvm_start_daemon.py	42.85%	4 Missing ⚠️
qubesadmin/tools/qvm_pool_legacy.py	0.00%	3 Missing ⚠️
qubesadmin/backup/core3.py	0.00%	2 Missing ⚠️
qubesadmin/tools/qvm_create.py	0.00%	2 Missing ⚠️
qubesadmin/tools/qvm_ls.py	66.66%	2 Missing ⚠️
qubesadmin/tools/qvm_run.py	50.00%	2 Missing ⚠️
... and 10 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #427      +/-   ##
==========================================
- Coverage   76.07%   76.04%   -0.03%     
==========================================
  Files          53       53              
  Lines        9286     9277       -9     
==========================================
- Hits         7064     7055       -9     
  Misses       2222     2222              

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[marmarek]

Before doing more tree-wide changes, I'd prefer remaining PRs that will need backporting to be finished first (especially #400).

[hippalectryon-0]

Makes sense !
Ping me when you think it's the right time to integrate the present PR, I'll rebase on main and re-run pyupgradeto make sure new changes are also 3.10-upgraded.