OpenAPI: use ':' instead of '#' to separate parts of a component path

[swallez]

Some tools do not accept a # in component path identifiers. This PR changes it to a : which is already used to separate namespace and name in type names.

Fixes #4183

Docs team: does this have any impact on documentation generation?

[lcawl]

I verified that none of the overlays are affected by this change and the docs output LGTM

[github-actions]

The backport to 8.x 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-8.x 8.x
# Navigate to the new working tree
cd .worktrees/backport-8.x
# Create a new branch
git switch --create backport-4184-to-8.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 dbb89db180052524cab77d324be4f0c00972807a
# Push it to GitHub
git push --set-upstream origin backport-4184-to-8.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.x

Then, create a pull request where the base branch is 8.x and the compare/head branch is backport-4184-to-8.x.

[github-actions]

The backport to 8.18 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-8.18 8.18
# Navigate to the new working tree
cd .worktrees/backport-8.18
# Create a new branch
git switch --create backport-4184-to-8.18
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 dbb89db180052524cab77d324be4f0c00972807a
# Push it to GitHub
git push --set-upstream origin backport-4184-to-8.18
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.18

Then, create a pull request where the base branch is 8.18 and the compare/head branch is backport-4184-to-8.18.

[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-4184-to-9.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 dbb89db180052524cab77d324be4f0c00972807a
# Push it to GitHub
git push --set-upstream origin backport-4184-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-4184-to-9.0.