refactor(schema): freeze v4beta14, bump latest to v4beta15

Snapshots pkg/skaffold/schema/latest into pkg/skaffold/schema/v4beta14
with an identity Upgrade() function, adds the v4beta14 entry to
schema.SchemaVersionsV1, flips the latest config.go guard comment from
'already released' to 'SAFE TO MODIFY', and bumps Version to
skaffold/v4beta15.

All sample skaffold.yaml files under integration/examples/ are bumped
to apiVersion: skaffold/v4beta15 (examples/ stays on v4beta14 per the
repo convention that /examples uses the latest released version).

Regenerates JSON schemas under docs-v[12]/content/en/schemas/ and the
CLI reference doc at docs-v2/content/en/docs/references/cli/_index.md.

This commit is purely mechanical; no behaviour change.

Author: bogdannazarenko

docs-v2/config.toml

@@ -86,7 +86,7 @@ weight = 1
 copyright = "Skaffold Authors"
 privacy_policy = "https://policies.google.com/privacy"
 github_repo = "https://github.com/GoogleContainerTools/skaffold"
-skaffold_version = "skaffold/v4beta14"
+skaffold_version = "skaffold/v4beta15"
 
 # Google Custom Search Engine ID. Remove or comment out to disable search.
 # gcs_engine_id = "013756393218025596041:3nojel67sum"

docs-v2/content/en/docs/references/cli/_index.md

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 metadata:
   name: hello

docs-v2/content/en/schemas/v4beta15.json

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 build:
   artifacts:

integration/examples/bazel/skaffold.yaml

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 build:
   artifacts:

integration/examples/buildpacks-java/skaffold.yaml

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 build:
   artifacts:

integration/examples/buildpacks-node/skaffold.yaml

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 build:
   artifacts:

integration/examples/buildpacks-python/skaffold.yaml

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 build:
   artifacts:

integration/examples/buildpacks/skaffold.yaml

@@ -1,4 +1,4 @@
-apiVersion: skaffold/v4beta14
+apiVersion: skaffold/v4beta15
 kind: Config
 build:
   platforms: ["linux/amd64", "linux/arm64"]