Add config for progress bars

[nik-rev]

Description

This PR:

• Allows to customize the progress bar characters used via styles.widgets.progress_bar_chars
• Makes the progress bars more precise by using a larger range of unicode characters: ['▏', '▎', '▍', '▌', '▋', '▊', '▉', '█'], instead of |. This also makes them look smoother

Issue

None

Testing

• Run cargo test progress_bar
• Open with cargo run --basic and observe

Tested platforms:

• Windows
• _macOS
• _Linux (Arch Linux)
• _Other

Checklist

Ensure all of these are met:

• If this is a code change, areas your change affects have been linted using (cargo fmt)
• If this is a code change, your changes pass cargo clippy --all -- -D warnings
• If this is a code change, new tests were added if relevant
• If this is a code change, your changes pass cargo test
• The change has been tested to work (see above) and doesn't appear to break other things
• Documentation has been updated if needed (README.md, help menu, docs, configs, etc.)
• There are no merge conflicts
• You have reviewed the changes first
• The pull request passes the provided CI pipeline

[codecov]

Codecov Report

❌ Patch coverage is 81.03448% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.44%. Comparing base (b7fba3e) to head (28cb773).

Files with missing lines	Patch %	Lines
src/canvas/widgets/mem_basic.rs	0.00%	5 Missing ⚠️
src/canvas/components/pipe_gauge.rs	90.69%	4 Missing ⚠️
src/canvas/widgets/cpu_basic.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1947      +/-   ##
==========================================
+ Coverage   53.37%   53.44%   +0.06%     
==========================================
  Files         119      120       +1     
  Lines       16482    16528      +46     
==========================================
+ Hits         8797     8833      +36     
- Misses       7685     7695      +10     

Flag	Coverage Δ
macos-14	46.03% <81.03%> (+0.17%)	⬆️
ubuntu-latest	51.81% <81.03%> (+0.07%)	⬆️
windows-2022	45.58% <82.45%> (+0.19%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.