Revert slurp_image extraction for svg_load

* src/image.c (svg_load): Inline slurp_image code again, as it didn't
build in its current form.
Reported by Andreas Schwab <schwab@linux-m68k.org>.
10 jobs for master in 197 minutes and 42 seconds (queued for 11 seconds)
Status Job ID Name Coverage
  Build Images
failed #75080
build-image-inotify

02:18:40

 
  Normal
skipped #75081
test-all-inotify
 
  Platform Images
failed #75082
build-image-eglot

02:09:40

failed #75084
build-image-gnustep

00:03:48

failed #75083
build-image-tree-sitter

02:20:46

 
  Platforms
skipped #75085
test-eglot
skipped #75087
test-gnustep
skipped #75086
test-tree-sitter
 
  Native Comp Images
passed #75088
build-native-comp-speed2

02:23:50

 
  Native Comp
failed #75089
test-native-comp-speed2

00:53:41

 
Name Stage Failure
failed
test-native-comp-speed2 Native Comp
Uploading artifacts for failed job
Uploading artifacts...
test-native-comp-speed2-505c8062/: found 531 matching files and directories

Uploading artifacts as "archive" to coordinator... 201 Created
id=75089 responseStatus=201 Created token=5sA4RZQa
Uploading artifacts...
test-native-comp-speed2-505c8062/junit-test-report.xml: found 1 matching files and directories

Uploading artifacts as "junit" to coordinator... 201 Created
id=75089 responseStatus=201 Created token=5sA4RZQa
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 2

failed
build-image-tree-sitter Platform Images
net/http: request canceled (Client.Timeout exceeded while awaiting headers)
Running after_script
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-tree-sitter-505c8062: No such file or directory
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

failed
build-image-inotify Build Images
78043d3b2659: Retrying in 1 second
0b23d1f31482: Pushed
context deadline exceeded (Client.Timeout exceeded while awaiting headers)
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-inotify-505c8062: No such file or directory
ERROR: Job failed: exit code 1
failed
build-image-eglot Platform Images
net/http: request canceled (Client.Timeout exceeded while awaiting headers)
Running after_script
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-eglot-505c8062: No such file or directory
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

failed
build-image-gnustep Platform Images
 > [internal] load build context:
------
rpc error: code = Canceled desc = grpc: the client connection is closing
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-gnustep-505c8062: No such file or directory
ERROR: Job failed: exit code 1