feature: support custom widget borders

[ClementTsang]

Description

A description of the change, what it does, and why it was made. If relevant (such as any change that modifies the UI), please provide screenshots of the changes:

Support setting custom border types. This doesn't support "no" borders for now, since I need to come up with a nice way of making it look good - I'll likely incorporate #1470 as the closest thing.

Examples

Normal:

Rounded corners:

Double lines:

Thick:

Issue

If applicable, what issue does this address?

Closes: #

Testing

If relevant, please state how this was tested. All changes must be tested to work:

If this is a code change, please also indicate which platforms were tested:

• Windows
• macOS
• Linux

Checklist

If relevant, ensure the following have been met:

• Areas your change affects have been linted using rustfmt (cargo fmt)
• The change has been tested and doesn't appear to cause any unintended breakage
• Documentation has been added/updated if needed (README.md, help menu, doc pages, etc.)
• The pull request passes the provided CI pipeline
• There are no merge conflicts
• If relevant, new tests were added (don't worry too much about coverage)

[codecov]

Codecov Report

Attention: Patch coverage is 28.07571% with 228 lines in your changes missing coverage. Please review.

Project coverage is 42.07%. Comparing base (1fe17dd) to head (ca39bde).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/canvas/widgets/process_table.rs	0.00%	36 Missing ⚠️
src/canvas/widgets/battery_display.rs	16.66%	35 Missing ⚠️
src/canvas/components/data_table/draw.rs	0.00%	24 Missing ⚠️
src/options/config/style/borders.rs	0.00%	21 Missing ⚠️
src/canvas/dialogs/dd_dialog.rs	0.00%	18 Missing ⚠️
src/canvas/widgets/network_graph.rs	0.00%	18 Missing ⚠️
src/canvas/widgets/mem_basic.rs	0.00%	11 Missing ⚠️
src/canvas/drawing_utils.rs	47.36%	10 Missing ⚠️
src/canvas/dialogs/help_dialog.rs	0.00%	9 Missing ⚠️
src/canvas/widgets/mem_graph.rs	0.00%	9 Missing ⚠️
... and 9 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1642      +/-   ##
==========================================
+ Coverage   42.03%   42.07%   +0.04%     
==========================================
  Files         116      117       +1     
  Lines       17625    17569      -56     
==========================================
- Hits         7409     7393      -16     
+ Misses      10216    10176      -40     

Flag	Coverage Δ
macos-14	37.39% <18.92%> (-0.07%)	⬇️
ubuntu-latest	43.87% <28.07%> (+0.05%)	⬆️
windows-2019	37.32% <18.98%> (-0.07%)	⬇️

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.