feat(form controls): add support for control sizing of b-form-file, b-form-checkbox, and b-form-radio (closes #3745)

[tmorehouse]

Describe the PR

Adds ability to specify size (sm or lg) to the following custom controls:

• b-form-file (uses custom SCSS)
• b-form-radio (uses custom SCSS)
• b-form-checkbox (uses custom SCSS)

Bootstrap v4.x most likely wont include custom-control sizes (except for custom-select for which sizes are currently supported), while bootstrap v5 will.

For form-file, radios and checks, it uses the custom classes b-custom-control-sm and b-custom-control-lg for controlling sizing.

Closes #3745

To Do:

• form-file docs update
• form-checkbox docs update
• form-radio docs update
• input-group docs update (showing custom checks, radios, and switches as addons)

PR checklist

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Enhancement
• ARIA accessibility
• Documentation update
• Other (please describe)

Does this PR introduce a breaking change? (check one)

• No
• Yes (please describe)

The PR fulfills these requirements:

• It's submitted to the dev branch, not the master branch
• When resolving a specific issue, it's referenced in the PR's title (i.e. [...] (fixes #xxx[,#xxx]), where "xxx" is the issue number)
• It should address only one issue or feature. If adding multiple features or fixing a bug and adding a new feature, break them into separate PRs if at all possible.
• The title should follow the Conventional Commits naming convention (i.e. fix(alert): not alerting during SSR render, docs(badge): update pill examples, fix typos, chore: fix typo in README, etc). This is very important, as the CHANGELOG is generated from these messages.

If new features/enhancement/fixes are added or changed:

• Includes documentation updates (including updating the component's package.json for slot and event changes)
• Includes any needed TypeScript declaration file updates
• New/updated tests are included and passing (if required)
• Existing test suites are passing
• The changes have not impacted the functionality of other components or directives
• ARIA Accessibility has been taken into consideration (Does it affect screen reader users or keyboard only users? Clickable items should be in the tab index, etc.)

If adding a new feature, or changing the functionality of an existing feature, the PR's
description above includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

[codecov]

Codecov Report

Merging #3794 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #3794   +/-   ##
=======================================
  Coverage   99.29%   99.29%           
=======================================
  Files         224      224           
  Lines        4391     4391           
  Branches     1244     1244           
=======================================
  Hits         4360     4360           
  Misses         25       25           
  Partials        6        6

Impacted Files	Coverage Δ
src/mixins/form-radio-check.js	100% <ø> (ø)	⬆️
src/components/form-file/form-file.js	95.83% <ø> (ø)	⬆️

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