ci: Unify workflows into singular pipeline

[rschristian]

Currently, we run 3 separate pipelines for each PR (assuming the PR touches source JS, we do have a bit of filtering in play):

• CI - builds, lints & tests, packages Preact
• Benchmarks - CI workflow, sets up source & current Preact tarballs, runs benches
• Compressed Size

As such, we're running the CI workflow twice (once directly, once called from Benchmarks) which, while not necessarily problematic as it's done in parallel, can be a bit noisy in the case of build/test failures (each will notify of failure separately) and is duplicated work at the very least. 3 separate pipelines is also a bit messy if you need to jump into the 'Actions' tab to check/compare different runs -- far from a major problem, but less than ideal IMO.

---

The idea here is to unify the aforementioned workflows into a singular pipeline; we'll get an overview of all jobs at once, make the control flow a bit more obvious & easier to edit, and skip some duplicated work. ci.yml will therefore be the orchestrator, triggering the runs of build-test.yml, benchmarks.yml, & size.yml, they'll no longer be entrypoints/pipelines themselves.

Workflow run in pic

[coveralls]

coverage: 99.488%. remained the same
when pulling 9c565bb on ci/refactor
into ad3bc3b on main.

[github-actions]

Size Change: 0 B

Total Size: 62 kB

ℹ️ View Unchanged

Filename	Size
compat/dist/compat.js	4.11 kB
compat/dist/compat.module.js	4.04 kB
compat/dist/compat.umd.js	4.18 kB
debug/dist/debug.js	3.82 kB
debug/dist/debug.module.js	3.83 kB
debug/dist/debug.umd.js	3.9 kB
devtools/dist/devtools.js	260 B
devtools/dist/devtools.module.js	274 B
devtools/dist/devtools.umd.js	346 B
dist/preact.js	4.66 kB
dist/preact.min.js	4.69 kB
dist/preact.min.module.js	4.68 kB
dist/preact.min.umd.js	4.71 kB
dist/preact.module.js	4.67 kB
dist/preact.umd.js	4.73 kB
hooks/dist/hooks.js	1.53 kB
hooks/dist/hooks.module.js	1.56 kB
hooks/dist/hooks.umd.js	1.6 kB
jsx-runtime/dist/jsxRuntime.js	981 B
jsx-runtime/dist/jsxRuntime.module.js	956 B
jsx-runtime/dist/jsxRuntime.umd.js	1.06 kB
test-utils/dist/testUtils.js	451 B
test-utils/dist/testUtils.module.js	456 B
test-utils/dist/testUtils.umd.js	536 B

_{compressed-size-action}

[rschristian]

The required status checks in the repo will need to be altered if this is to land; Build & Test is no longer ran directly, so the status will never be reported.