feat(terraform): add PREFIX and SUFFIX settings to `tf_prompt_info` (#8605)

Closes #8605

plugins/terraform/terraform.plugin.zsh

 function tf_prompt_info() {
-    # dont show 'default' workspace in home dir
-    [[ "$PWD" == ~ ]] && return
-    # check if in terraform dir
-    if [[ -d .terraform && -r .terraform/environment  ]]; then
-      workspace=$(cat .terraform/environment) || return
-      echo "[${workspace}]"
-    fi
+  # dont show 'default' workspace in home dir
+  [[ "$PWD" != ~ ]] || return
+  # check if in terraform dir and file exists
+  [[ -d .terraform && -r .terraform/environment ]] || return
+
+  local workspace="$(< .terraform/environment)"
+  echo "${ZSH_THEME_TF_PROMPT_PREFIX-[}${workspace:gs/%/%%}${ZSH_THEME_TF_PROMPT_SUFFIX-]}"
 }
 
 alias tf='terraform'