chore(updatecli): track JDK21 version in Dockerfiles

[lemeurherve]

This changes restores the target updating all Dockerfiles for the main JDK (21).

Ref:

• Use JAVA_VERSION that is consistent with docker-bake file #2334 (comment)

Testing done

CI

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• Ensure that the pull request title represents the desired changelog entry
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[dduportal]

LGTM! the CI checks shows the new targets will update the expected ARG values:

target: setJDK21Version
-----------------------

Repository	: github.com/jenkinsci/docker@master

[transformers]
✔ Result correctly transformed from "21.0.11+10" to "21.0.11_10"
⚠ The line #5, matched by the keyword "ARG" and the matcher "JAVA_VERSION", is changed from "ARG JAVA_VERSION=21.0.10_7" to "ARG JAVA_VERSION=21.0.11_10".
⚠ The line #8, matched by the keyword "ARG" and the matcher "JAVA_VERSION", is changed from "ARG JAVA_VERSION=21.0.10_7" to "ARG JAVA_VERSION=21.0.11_10".
⚠ The line #5, matched by the keyword "ARG" and the matcher "JAVA_VERSION", is changed from "ARG JAVA_VERSION=21.0.10_7" to "ARG JAVA_VERSION=21.0.11_10".
⚠ The line #4, matched by the keyword "ARG" and the matcher "JAVA_VERSION", is changed from "ARG JAVA_VERSION=21.0.10_7" to "ARG JAVA_VERSION=21.0.11_10".
⚠ The line #12, matched by the keyword "ARG" and the matcher "JAVA_VERSION", is changed from "ARG JAVA_VERSION=21.0.10_7" to "ARG JAVA_VERSION=21.0.11_10".
⚠ - changed lines [5] of file "alpine/hotspot/Dockerfile", changed lines [8] of file "debian/Dockerfile", changed lines [5] of file "rhel/Dockerfile", changed lines [4 12] of file "windows/windowsservercore/hotspot/Dockerfile"

and no regression on the existing target:

target: setJDK21VersionDockerBake
---------------------------------

Repository	: github.com/jenkinsci/docker@master

[transformers]
✔ Result correctly transformed from "21.0.11+10" to "21.0.11_10"
✔ - no changes detected:
	path "variable.JAVA21_VERSION.default" already set to "21.0.11_10", from file "docker-bake.hcl", 

[dduportal]

FTR, updated title and labels:

• It's a chore and not fix (does not change anything on the built artifacts, it's only tooling change with no user-facing direct impact)
  -The title was mentioning a JDK21 update, but it only adds targets to updatecli jdk21 manifest. Update accordingly.