(#9400 P2b) host: docker: replace seven echo|grep subshells with here-strings

Seven near-identical `echo "${DOCKER_INFO}" | grep -i -e <key>: | cut -d : -f 2 | xargs echo -n`
chains parse fields out of cached `docker info` output. Replace each with
`grep -i -e <key>: <<< "${DOCKER_INFO}" | cut -d : -f 2 | xargs echo -n`.

The here-string and `echo "${DOCKER_INFO}"` produce the same bytes on
stdin (one trailing newline), so grep, cut and xargs see identical input
and emit the same field value. The change drops one subshell + one echo
process per invocation; `get_docker_info_once` runs these in a tight
sequence at the top of every Docker-mode build.

Part of #9400 (P2b).

Assisted-by: Claude:claude-opus-4.7

Author: iav

lib/functions/host/docker.sh

@@ -192,26 +192,26 @@ function docker_cli_prepare() {
 	# Detect some docker info; use cached.
 	get_docker_info_once
 
-	DOCKER_SERVER_VERSION="$(echo "${DOCKER_INFO}" | grep -i -e "Server Version:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_SERVER_VERSION="$(grep -i -e "Server Version:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Server version" "${DOCKER_SERVER_VERSION}" "debug"
 
-	DOCKER_SERVER_KERNEL_VERSION="$(echo "${DOCKER_INFO}" | grep -i -e "Kernel Version:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_SERVER_KERNEL_VERSION="$(grep -i -e "Kernel Version:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Server Kernel version" "${DOCKER_SERVER_KERNEL_VERSION}" "debug"
 
-	DOCKER_SERVER_TOTAL_RAM="$(echo "${DOCKER_INFO}" | grep -i -e "Total memory:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_SERVER_TOTAL_RAM="$(grep -i -e "Total memory:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Server Total RAM" "${DOCKER_SERVER_TOTAL_RAM}" "debug"
 
-	DOCKER_SERVER_CPUS="$(echo "${DOCKER_INFO}" | grep -i -e "CPUs:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_SERVER_CPUS="$(grep -i -e "CPUs:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Server CPUs" "${DOCKER_SERVER_CPUS}" "debug"
 
-	DOCKER_SERVER_OS="$(echo "${DOCKER_INFO}" | grep -i -e "Operating System:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_SERVER_OS="$(grep -i -e "Operating System:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Server OS" "${DOCKER_SERVER_OS}" "debug"
 
 	declare -g DOCKER_ARMBIAN_HOST_OS_UNAME
 	DOCKER_ARMBIAN_HOST_OS_UNAME="$(uname)"
 	display_alert "Local uname" "${DOCKER_ARMBIAN_HOST_OS_UNAME}" "debug"
 
-	DOCKER_BUILDX_VERSION="$(echo "${DOCKER_INFO}" | grep -i -e "buildx:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_BUILDX_VERSION="$(grep -i -e "buildx:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Buildx version" "${DOCKER_BUILDX_VERSION}" "debug"
 
 	declare -g DOCKER_HAS_BUILDX=no
@@ -222,7 +222,7 @@ function docker_cli_prepare() {
 	fi
 	display_alert "Docker has buildx?" "${DOCKER_HAS_BUILDX}" "debug"
 
-	DOCKER_SERVER_NAME_HOST="$(echo "${DOCKER_INFO}" | grep -i -e "name:" | cut -d ":" -f 2 | xargs echo -n)"
+	DOCKER_SERVER_NAME_HOST="$(grep -i -e "name:" <<< "${DOCKER_INFO}" | cut -d ":" -f 2 | xargs echo -n)"
 	display_alert "Docker Server Hostname" "${DOCKER_SERVER_NAME_HOST}" "debug"
 
 	# Gymnastics: under Darwin, Docker Desktop and Rancher Desktop in dockerd mode behave differently.