miscellaneous maintenance (mostly GHA)

[vszakats]

• add zizmor GHA linter job.
• add ruff to GHA linter job.
• set persist-credentials: false.
• drop permissions where missing.
• set GHA concurrency where missing.
• suppress zizmor warning for cancel-in-progress: false.
  Though perhaps it could be set to true?
• pages: replace hard-coded string with GitHub variable.
• sync action version numbers in comments.
• use full version numbers in newly added actions.
• page: scope extra permissions to the deploy job.
• silence zizmor warning about unpinned oss-fuzz action.
• avoid GitHub macros in shell code. Replace by envs.
• add name to each job to make them easier to read, and
  to silence pedantic zizmor.
• say why a job needs extra permissions. For zizmor.
• shell: add missing double quotes, drop unused variables, fix printf
  format string to be constant, fix other misc shellcheck warnings.
• move 'just_dependencies', 'PythonTests', 'Mainline' (2x) jobs from
  ci to a new local workflow, to not get triggered by curl/curl PR
  and master commits. These jobs either do not use the curl source repo,
  or use its master branch.
  To save 5 minutes CI time per curl/curl PR push.
• test_corpus_decoder.py: fix to indent consistently.
• fix issues reported by yamllint. (indent mostly)
• sync ruff configuration with other curl repos. Fix minor fallouts.
  Credits-to: Dan Fandrich
  curl/curl@57cc523
• make sure to always use pyproject.toml to install pip packages.
  To have all of them pinned.
• move pyproject.toml default packages to group to avoid installing
  them when unused.
• merge two pip invocations by adding a pinned pytest_playwright to the group.
• drop pip upgrades, use the version preinstalled on the host, for
  determinism.
• tidy-up python shebangs and exec attributes.
• tidy-up shell script shebangs and sets.
• delete copyright years.
• drop step name from well-known actions like checkout and python,
  to sync with other curl repos and making it more readily apparent
  what they are.
• pyproject.toml: use a single style to specify dependency versions.
• cmake: drop redundant DEFINED ENV checks.
• cmake: drop appending CFLAGS, CXXFLAGS envs manually. CMake uses
  these automatically.
  https://cmake.org/cmake/help/latest/envvar/CFLAGS.html
  https://cmake.org/cmake/help/latest/envvar/CXXFLAGS.html
• cmake: check if empty is non-empty, vs. just defined.
• cmake: fold long lines.
• whitespace.

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w/o sp https://github.com/curl/curl-fuzzer/pull/214/files?w=1