gh-37351: CI: Update Linux platforms / runners, remove `ubuntu-trusty`, `opensuse-{15.3,15.4}`
    
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We increase parallelization according to [the upgraded Linux runners on
GH Actions](https://docs.github.com/en/actions/using-github-hosted-
runners/about-github-hosted-runners/about-github-hosted-
runners#standard-github-hosted-runners-for-public-repositories) (4 CPUs)
and add some newer platforms.

`fedora-40` fails because we reject GCC 14, that's now tracked in
#37353.

Update (Apr 2024):
- ubuntu-trusty reaches EOL, we drop it. Also remove some past-EOL
OpenSUSE Leap; see #32074
- also reducing the list of systems tested with `--enable-system-site-
packages` because there is no interest in doing the porting work
- updating the default platform (used by the incremental build
workflows) from `ubuntu-focal` to `ubuntu-jammy`.

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URL: #37351
Reported by: Matthias Köppe
Reviewer(s): Julian Rüth, Kwankyu Lee, Matthias Köppe, Michael Orlitzky, Tobias Diez

Author: Release Manager

.devcontainer/portability-ubuntu-trusty-toolchain-gcc_9-minimal/devcontainer.json renamed to .devcontainer/portability-fedora-40-minimal/devcontainer.json

@@ -3,12 +3,12 @@
 //      from .devcontainer/portability-devcontainer.json.in
 // See https://aka.ms/devcontainer.json for format details.
 {
-    "name": "ubuntu-trusty-toolchain-gcc_9-minimal (≥ 8-core)",
+    "name": "fedora-40-minimal (≥ 8-core)",
     "build": {
         "dockerfile": "portability-Dockerfile",
         // See tox.ini for definitions
         "args": {
-            "SYSTEM_FACTOR": "ubuntu-trusty-toolchain-gcc_9",
+            "SYSTEM_FACTOR": "fedora-40",
             "PACKAGE_FACTOR": "minimal",
             "DOCKER_TARGET": "with-targets",
             "DOCKER_TAG": "dev"

.devcontainer/portability-opensuse-15.3-gcc_11-python3.9-minimal/portability-Dockerfile renamed to .devcontainer/portability-fedora-40-minimal/portability-Dockerfile

@@ -3,12 +3,12 @@
 //      from .devcontainer/portability-devcontainer.json.in
 // See https://aka.ms/devcontainer.json for format details.
 {
-    "name": "ubuntu-trusty-toolchain-gcc_9-standard (≥ 8-core)",
+    "name": "fedora-40-standard (≥ 8-core)",
     "build": {
         "dockerfile": "portability-Dockerfile",
         // See tox.ini for definitions
         "args": {
-            "SYSTEM_FACTOR": "ubuntu-trusty-toolchain-gcc_9",
+            "SYSTEM_FACTOR": "fedora-40",
             "PACKAGE_FACTOR": "standard",
             "DOCKER_TARGET": "with-targets",
             "DOCKER_TAG": "dev"

.devcontainer/portability-ubuntu-trusty-toolchain-gcc_9-standard/devcontainer.json renamed to .devcontainer/portability-fedora-40-standard/devcontainer.json

@@ -3,12 +3,12 @@
 //      from .devcontainer/portability-devcontainer.json.in
 // See https://aka.ms/devcontainer.json for format details.
 {
-    "name": "opensuse-15.3-gcc_11-python3.9-minimal (≥ 8-core)",
+    "name": "gentoo-python3.12-minimal (≥ 8-core)",
     "build": {
         "dockerfile": "portability-Dockerfile",
         // See tox.ini for definitions
         "args": {
-            "SYSTEM_FACTOR": "opensuse-15.3-gcc_11-python3.9",
+            "SYSTEM_FACTOR": "gentoo-python3.12",
             "PACKAGE_FACTOR": "minimal",
             "DOCKER_TARGET": "with-targets",
             "DOCKER_TAG": "dev"

.devcontainer/portability-opensuse-15.3-gcc_11-python3.9-standard/portability-Dockerfile renamed to .devcontainer/portability-fedora-40-standard/portability-Dockerfile

@@ -3,12 +3,12 @@
 //      from .devcontainer/portability-devcontainer.json.in
 // See https://aka.ms/devcontainer.json for format details.
 {
-    "name": "opensuse-15.3-gcc_11-python3.9-standard (≥ 8-core)",
+    "name": "gentoo-python3.12-standard (≥ 8-core)",
     "build": {
         "dockerfile": "portability-Dockerfile",
         // See tox.ini for definitions
         "args": {
-            "SYSTEM_FACTOR": "opensuse-15.3-gcc_11-python3.9",
+            "SYSTEM_FACTOR": "gentoo-python3.12",
             "PACKAGE_FACTOR": "standard",
             "DOCKER_TARGET": "with-targets",
             "DOCKER_TAG": "dev"

.devcontainer/portability-opensuse-15.3-gcc_11-python3.9-minimal/devcontainer.json renamed to .devcontainer/portability-gentoo-python3.12-minimal/devcontainer.json

@@ -3,12 +3,12 @@
 //      from .devcontainer/portability-devcontainer.json.in
 // See https://aka.ms/devcontainer.json for format details.
 {
-    "name": "opensuse-15.4-gcc_11-python3.10-minimal (≥ 8-core)",
+    "name": "linuxmint-21.3-minimal (≥ 8-core)",
     "build": {
         "dockerfile": "portability-Dockerfile",
         // See tox.ini for definitions
         "args": {
-            "SYSTEM_FACTOR": "opensuse-15.4-gcc_11-python3.10",
+            "SYSTEM_FACTOR": "linuxmint-21.3",
             "PACKAGE_FACTOR": "minimal",
             "DOCKER_TARGET": "with-targets",
             "DOCKER_TAG": "dev"