- Also switch in cases where we have a subset that is likely significantly smaller and hence quicker to sort

Switch to requiring EXTENDED_READ permission for access to NodeMonitor
data. It might theoretically be better if we had more granular
permissions on each NodeMonitor, but that's a bigger change, and since
EXTENDED_READ is already what we use to limit access to serving the
computer's config.xml, I think this is appropriate.

(cherry picked from commit c7fd90a8)

* Avoid deprecated findbugs annotations

* One more forgotten annotation

wait-node-online and wait-node-offline covered by test-cases

* no longer hard-code the icon for the executor panel

[FIXED JENKINS-36775]

* add documentation to Computer.java for custom icons

* add recommended implementation to the javadoc

* [JENKINS-34468] CLI command offline-node extracted from core to CLI

offline-node extended to accept multiple node names
offline-node covered by test-cases

* Fixed translation properties

* Fixes based on Oleg's comments

* Fixed HelpCommandTest test-case

* Minor fixes

* Uses Matchers.instanceOf everywhere instead of Java operator instanceof

* [JENKINS-35570] List of computer's names extracted to Util

Signed-off-by: NNicolas De Loof <nicolas.deloof@gmail.com>

* [JENKINS-31417] CLI command connect-node extracted from core to CLI

connect-node extended to accept multiple node names
connect-node covered by test-cases

* Slighty modified Javadoc

* Fixed translations after rebase

disconnect-node extended to accept multiple node names
disconnect-node covered by test-cases

Functionality was moved to OnlineNodeCommand class already

- Code that is running from a plugin and on the master's JVM is guaranteed to never get null from this method (any cases where you do get null are bugs in core)
- Code that is running from a plugin and on a remote JVM should never be allowed to load the Jenkins class in their classloader, so should never use Jenkins.getInstance()... we are annotating the method with @Nullable so that such code can have some evolution time
- Code that is running in core and on one of two special paths should use the Jenkins.getInstanceOrNull() method so that the UI can be presented to users before the singleton has been instantiated / after the singleton has been destroyed
- The remaining 95% of uses in core (and 100% of uses in plugins) can safely assume that the instance is never null

This reverts commit bb7c8fce.

Closes #2090, I'll redo this as a PR... though if that PR is subject to multiple rounds of review before being merged then I will take that of evidence of the exact problem that committing directly was supposed to resolve... namely exponentially multiplying the effort required to make actual improvements to the code base.

- It is never too late to do the right thing.
- The vast majority of usages of `Jenkins.getInstance()` in core currently assume that its return value is non-null
- This commit changes those that are written to correctly check for non-null values will call `Jenkins.getInstanceOrNull()`
- We deprecate the `Jenkins.getActiveInstance()` madness
- I checked with @kohsuke who said not to bother with a PR and just commit this strongly opinionated change direct to master as a PR will just degrade into a bikeshedding.

Computer.CREATE should be scoped to JENKINS, not COMPUTER, since it is checked on Jenkins, not a Node or Computer.
Compare Item.CREATE, scoped to ITEM_GROUP, not ITEM.

This change adds code to check that the user isn't attempting to rename
an existing node with the name of another existing node.  Previous to
this change, such rename operations would succeed and would corrupt node
configuration data.

(cherry picked from commit 16d6429c)

This change adds code to check that the user isn't attempting to rename
an existing node with the name of another existing node.  Previous to
this change, such rename operations would succeed and would corrupt node
configuration data.

online-node covered by test-cases

* moved to jenkins.util.SystemProperties
* consistent naming getString/getInteger/getBoolean
* improved code formatting
Improved JavaDoc

Accomplished by centralizing calls to System.getProperty(String) and related into new file SystemProperties.java.
There, we first check for existence of system property; if not, we look for property in context.xml
This is done for "application" properties (like hudson.DNSMultiCast.disabled) but not for java properties (like user.name)

- Also tidy up some of the mess logic in both #1866 and #1860

(cherry picked from commit d72d7b83)

Node objects are owned by the Nodes class not by Jenkins so NodeProperties
and anything modifiying them needs to be updated.  Also modifying Nodes
requires a lock on the Queue so use this lock not Jenkins to prevent the
deadlock observed in JENKINS-30057

(cherry picked from commit 06f690db)

Node objects are owned by the Nodes class not by Jenkins so NodeProperties
and anything modifiying them needs to be updated.  Also modifying Nodes
requires a lock on the Queue so use this lock not Jenkins to prevent the
deadlock observed in JENKINS-30057