Only add x-codeSamples extensions to docs builds of openapi

[miguelgrinberg]

This change moves the generation of the x-codeSamples OpenAPI extension to the docs-specific builds. The make transform-to-openapi-for-docs reruns the request converter on all examples, then regenerates schema.json so that the new examples are included. Then it calls the OpenAPI generator with the new --include-language-examples option to request that the x-codeSamples extension is included.

The regular OpenAPI builds do not include the new CLI option, so they will not have x-codeSamples. The make generate command does not regenerate examples anymore, since this is only needed for the docs workflow now.

In addition to the above, the generate-language-examples.js script was changed so that it performs a non-destructive update of the language examples. This is to allow code examples for other languages with no request converter support to be added manually, or through custom builds of the request converter, such as the one supporting Java.

[github-actions]

The backport to 9.0 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-9.0 9.0
# Navigate to the new working tree
cd .worktrees/backport-9.0
# Create a new branch
git switch --create backport-4582-to-9.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 688cb3447d94699a50f1ca5b89324caf922e11d5
# Push it to GitHub
git push --set-upstream origin backport-4582-to-9.0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-9.0

Then, create a pull request where the base branch is 9.0 and the compare/head branch is backport-4582-to-9.0.