aws: refactor AWS plugin (#7615)

* Update the AWS plugin to support disabling RPROMT display:
  Use a $SHOW_AWS_PROMPT option.

* Refactoring aws plugin:
  Exposing customizable aws_prompt_info function to be used in themes.

* Set aws prompt prefix and suffix to original values and fix README

Co-authored-by: "Vassilis S. Moustakas" <vsmoustakas@gmail.com>

plugins/aws/aws.plugin.zsh

@@ -1,14 +1,16 @@
+# AWS profile selection
+
 function agp {
   echo $AWS_PROFILE
 }
 
 function asp {
-  local rprompt=${RPROMPT/<aws:$AWS_PROFILE>/}
-
   export AWS_DEFAULT_PROFILE=$1
   export AWS_PROFILE=$1
 
-  export RPROMPT="<aws:$AWS_PROFILE>$rprompt"
+  if [[ -z "$1" ]]; then
+    echo AWS profile cleared.
+  fi
 }
 
 function aws_profiles {
@@ -17,6 +19,18 @@ function aws_profiles {
 compctl -K aws_profiles asp
 
 
+# AWS prompt
+
+function aws_prompt_info() {
+  [[ -z $AWS_PROFILE ]] && return
+  echo "${ZSH_THEME_AWS_PREFIX:=<aws:}${AWS_PROFILE}${ZSH_THEME_AWS_SUFFIX:=>}"
+}
+
+if [ "$SHOW_AWS_PROMPT" != false ]; then
+  export RPROMPT='$(aws_prompt_info)'"$RPROMPT"
+fi
+
+
 # Load awscli completions
 
 _awscli-homebrew-installed() {