Add an AWS module with aws-info function

[tagatac]

Fixes #2107

Proposed Changes

• Add an AWS module.
• Activate command completion per the user guide.
• Add a function that fetches the active AWS profile and region and exposes them as variables for use in RPROMPT.

See an example usage here: tagatac@129bb9c

ohmyzsh reference: https://github.com/ohmyzsh/ohmyzsh/tree/9151236d1e0cb64b2e803d7ec1736c7a717efc33/plugins/aws

Heavily assisted by Claude Code.

[tagatac]

Cc: @sorin-ionescu @rjcoelho

[tagatac]

@belak, it seems like you have the best grasp on the usefulness threshold for new modules. Do you think this module belongs here or in prezto-contrib? AWS seems pretty ubiquitous to me, but I may be biased.

[tagatac]

@indrajitr WDYT?