feat: select target to build depending on the requirement of the modified files

[lemeurherve]

This PR allows to build:

• Only infra.ci.jenkins.io image variant if only plugins-infra.ci.jenkins.io.txt if modified (with the update-plugins GHA)
• Only weekly.ci.jenkins.io image variant if only plugins-weekly.ci.jenkins.io.txt if modified (with the update-plugins GHA)
• Both image variants there is more than one of these files among a list of files requiring a build
• No image variant build if none of the modified file(s) is requiring a build

Tested with replays in #1470 by alternating the modified files in that PR:

• Success with only infra-ci target, only variant built:

  • Modified files: README.md, plugins-infra.ci.jenkins.io.txt
  • https://infra.ci.jenkins.io/job/docker-jobs/job/docker-jenkins-weekly/job/PR-1470/48/
  • Corresponding commit: 091c4c9

• Success with only weekly-ci target, only variant built:

  • Modified files: README.md, plugins-weekly.ci.jenkins.io.txt
  • https://infra.ci.jenkins.io/job/docker-jobs/job/docker-jenkins-weekly/job/PR-1470/50/
  • Corresponding commit: c761702

• Success with docker-bake.hcl modified (one of the files requiring a build), both variants built:

  • Modified files: README.md, docker-bake.hcl
  • https://infra.ci.jenkins.io/job/docker-jobs/job/docker-jenkins-weekly/job/PR-1470/54/
  • Corresponding commit: 834150c

• Success with none of the modified files requiring a build, no variant built:

  • Modified files: README.md
  • https://infra.ci.jenkins.io/job/docker-jobs/job/docker-jenkins-weekly/job/PR-1470/52/
  • Corresponding commit: 3060fb1

It also allows to create distinct plugins update pull requests depending on which plugins list is updated.

Ref:

• Split docker-jenkins-weekly and docker-jenkins-weekly.ci for infra.ci and weekly.ci helpdesk#3887

[lemeurherve]

The merge of this PR on main has correctly triggered a build of both variants: https://infra.ci.jenkins.io/job/docker-jobs/job/docker-jenkins-weekly/job/main/365/

And the GHA has correctly opened two distinct pull requests:

• chore(deps): update infra.ci.jenkins.io plugins #1476
• chore(deps): update weekly.ci.jenkins.io plugins #1477

Finally, these pull requests have themselves correctly triggered a build of only their corresponding variant.

[lemeurherve]

From jenkins-infra/helpdesk#3887 (comment):

Note that running the last-weekly GHA results in a unique pull request containing the Jenkins version update and both plugins lists update, as both should be updated every time the Jenkins version changes:

• feat(deps): bump jenkins weekly to 2.441 #1478