fix(ApplicationCommandOptions): clean up code for builder options

[vladfrangu]

Please describe the changes this PR makes and why it should be merged:

The previous code was really messy, especially since the types in discord-api-types became much stricter. This PR helps cleanup the internal code by making certain features (like choices) mixins instead of classes you extend directly.

Status and versioning classification:

• Code changes have been tested, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating
• This PR changes the library's interface (methods or parameters added)
• This PR includes breaking changes (methods removed or renamed, parameters moved or removed)

[codecov-commenter]

Codecov Report

Merging #68 (a6f6d92) into main (a9addd5) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #68   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        21    -1     
  Lines          291       306   +15     
  Branches        37        42    +5     
=========================================
+ Hits           291       306   +15     

Impacted Files	Coverage Δ
src/interactions/slashCommands/Assertions.ts	100.00% <ø> (ø)
.../interactions/slashCommands/SlashCommandBuilder.ts	100.00% <ø> (ø)
.../slashCommands/mixins/SharedSlashCommandOptions.ts	100.00% <ø> (ø)
...eractions/slashCommands/SlashCommandSubcommands.ts	100.00% <100.00%> (ø)
...ashCommands/mixins/ApplicationCommandOptionBase.ts	100.00% <100.00%> (ø)
...ixins/ApplicationCommandOptionChannelTypesMixin.ts	100.00% <100.00%> (ø)
...ionCommandOptionWithChoicesAndAutocompleteMixin.ts	100.00% <100.00%> (ø)
src/interactions/slashCommands/options/boolean.ts	100.00% <100.00%> (ø)
src/interactions/slashCommands/options/channel.ts	100.00% <100.00%> (ø)
src/interactions/slashCommands/options/integer.ts	100.00% <100.00%> (ø)
... and 5 more

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