Update Jenkins core and plugins: 2021Q2 edition

Last time: #17730 (closed)

Steps:

• Scrutinize changelogs, paying special attention to changes on how agents connect to controller.
• Maybe change how agents connect to controller: #17798 (closed) (will to this in the context of #17846 (closed))
• Fix issue with APT proxy not being able to handle redirections: #17797 (closed)
• Update Jenkins.
• Update plugins.
• Restart all agents.
• Update jobs manually (may be needed so XML is valid with current Jenkins): /usr/local/sbin/deploy_jenkins_jobs update
• Restart builds that were interrupted by Jenkins restart
• Go through warnings in Jenkins interface.
• Manually remove removed plugins or fix Puppet code to do this automatically. (will do in the context of #17847 (closed))
• Create a list of plugins actively/directly used by Tails. (will do in the context of #17847 (closed))
• Schedule next update. #17847 (closed)

Upgrade info

• Current Jenkins version: 2.263.3
• Latest Jenkins version available in Debian: 2.289.2

From changelog and changelog-old, points of attention from 2.263 → 2.289(current latest):

• 2.264: Change the standard URL for obtaining the Inbound Agent configuration file from ${agent_url}/slave-agent.jnlp to ${agent_url}/jenkins-agent.jnlp. The old name is obsolete and will be removed at a future time. (issue 35452)
• 2.266: Spring and XStream updates (breaking changes) -- "It is a good idea to update all your plugins before upgrading Jenkins core." -- Compatibility of plugins manually checked and confirmed.
• 2.276: Add a system property jenkins.agent.inboundUrl to provide an alternate URL for inbound TCP agents. (issue 63222) (FTR only)
• 2.282: SSHD module is no longer bundled in Jenkins core. Provide SSHD as a plugin. I checked, it's bundled with the .deb package
• 2.284: Stop bundling the Ant and Javadoc plugins. (FTR: we have javadoc turned on)

Plugins

Plugins download URL: https://updates.jenkins.io/download/plugins/

Plugin (machine name)	New version	Current version	Obs	Minimum Jenkins version	Missing dependencies
antisamy-markup-formatter	2.1	1.1	Incompatible
Apache-httpcomponents-client-4-api	4.5.13-1.0	4.5.10-2.0
bootstrap4-api	4.6.0-3	4.5.3-1
bouncycastle-api	2.20	2.16.0
checks-api	1.7.2	1.1.1
cloudbees-folder	6.15	6.14
command-launcher	1.6	1.2
conditional-buildstep	1.4.1	1.4.0
copyartifact	1.46.1	1.45.3
credentials	2.5	2.3.14
cucumber-reports	5.5.0	5.4.0
display-url-api	2.3.5	2.3.4
durable-task	1.37	1.35	1.38 available		sshd >= 3.0.1
echarts-api	5.1.2-3	4.9.0-2
email-ext	2.83	2.80
envinject	2.4.0	2.3.0	Unavailable	2.264
font-awesome-api	5.15.3-4	5.15.1-1
git	4.7.2	4.4.5
git-client	3.8.0	3.5.1
icon-shim	3.0.0	2.0.3	Unavailable / Deprecated	2.269	sshd >= 3.0.1
jackson2-api	2.12.3	2.12.0
jdk-tool	1.5	1.0
jquery3-api	3.6.0-2	3.5.1-2
junit	1.51	1.45
mailer	1.34	1.32.1
matrix-auth	2.6.7	2.6.4
matrix-project	1.19	1.18	Unavailable		junit >= 1.47
maven-plugin	3.12	3.8	Unavailable		apache-httpcomponents-client-4-api >= 4.5.13-1.0; junit >= 1.48
parameterized-trigger	2.41	2.39	Unavailable		conditional-buildstep >= 1.4.1; script-security >= 1.77
plugin-util-api	2.4.0	1.5.0
popper-api	1.16.1-2	1.16.0-7
postbuildscript	3.0.0	2.11.0	Unavailable		matrix-project >= 1.18
PrioritySorter	4.0.0	3.6.0
resource-disposer	0.16	0.14
run-condition	1.5	1.3
script-security	1.77	1.75
simple-theme-plugin	0.7	0.6
snakeyaml-api	1.29.1	1.27.0
ssh-credentials	1.19	1.18.1	Unavailable		credentials >= 2.5; trilead-api >= 1.0.13
structs	1.23	1.20
timestamper	1.13	1.11.8
token-macro	2.13	2.12
trilead-api	1.0.13	1.0.12
windows-slaves	1.8	1.0
workflow-api	2.46	2.40
workflow-durable-task-step	2.39	2.37
workflow-scm-step	2.13	2.11
workflow-step-api	2.24	2.23
workflow-support	3.8	3.7
ws-cleanup	0.39	0.38