fix(Layout): layout cache does not grow without bounds

[marianomarciello]

This pull request avoids the growth of Layout cache without any bounds.
The Layout cache is now using an LruCache (doc).
The current default cache size is set to 16. It seems reasonable for me to keep this value low.
A user can set the cache size during the Layout instantiation.

fix #402

[codecov]

Codecov Report

Merging #487 (064cf8e) into main (d4976d4) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #487      +/-   ##
==========================================
+ Coverage   89.89%   89.93%   +0.04%     
==========================================
  Files          41       41              
  Lines       11286    11334      +48     
==========================================
+ Hits        10145    10193      +48     
  Misses       1141     1141              

Files Changed	Coverage Δ
src/layout.rs	98.37% <100.00%> (+0.07%)	⬆️

[joshka]

LGTM - happy to merge this with or without the suggestions.

Edit: I just noticed the lint check - can you please run cargo make format and bump this.

[joshka]

Code is great.
Docs look good - thanks for adding these.

A couple of minor changes to make the docs render the DEFAULT_CACHE_SIZE. You might also need to rewrap the doc text if these changes are made. Check the VSCode Rewrap extension or configure your IDE / editor to wrap at 100 chars.

[joshka]

Thanks again for your contribution.

[joshka]

I rebased on main, squashed and updated the commit message so it would look nice in the Changelog and merged this.

fix(Layout): use LruCache for layout cache (#487)

The layout cache now uses a LruCache with default size set to 16 entries.
Previously the cache was backed by a HashMap, and was able to grow
without bounds as a new entry was added for every new combination of
layout parameters.

- Added a new method (`layout::init_cache(usize)`) that allows the cache
size to be changed if necessary. This will only have an effect if it is called
prior to any calls to `layout::split()` as the cache is wrapped in a `OnceLock`

Thanks for submitting this PR. We appreciate your contribution.