perf(yarn): skip `yarn` call if default global bin directory exists (#10290)

Fixes #10290

plugins/yarn/yarn.plugin.zsh

-# Add yarn bin directory to $PATH if it exists and not in $PATH already
-bindir=$(yarn global bin 2>/dev/null) \
+# Skip yarn call if default global bin dir exists
+[[ -d "$HOME/.yarn/bin" ]] && bindir="$HOME/.yarn/bin" || bindir="$(yarn global bin 2>/dev/null)"
+
+# Add yarn bin directory to $PATH if it exists and not already in $PATH
+[[ $? -eq 0 ]] \
   && [[ -d "$bindir" ]] \
   && (( ! ${path[(Ie)$bindir]} )) \
   && path+=("$bindir")