Changes

docs: update documents (#3288)

This pull request mainly focuses on updating the documentation for the
CI/CD configurations and organizing the structure of the documentation
files. The key changes include adding new sections, updating existing
information, and introducing new guides.

Documentation updates:

*
[`README.md`](diffhunk://#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5L22-R23):
Updated the directory structure and added new sections on deprecated
Jenkins job storage and the file structure for jobs and pipelines.
[[1]](diffhunk://#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5L22-R23)
[[2]](diffhunk://#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5R33-R91)
*
[`docs/README.md`](diffhunk://#diff-0b5ca119d2be595aa307d34512d9679e49186307ef94201e4b3dfa079aa89938R1-R37):
Added a comprehensive guide and references for using the project to
manage CI pipelines, including a table of contents.
* `docs/contributing.md`, `docs/core-concepts.md`,
`docs/designs/README.md`: Added "Work in Progress" (WIP) placeholders
for future content.
*
[`docs/guides/README.md`](diffhunk://#diff-8d80745b4e642475274e1de3100d73869664e9ed435af8f839eff86b39acbbedR1-R9):
Introduced a new section for CI guides with detailed documentation and
tutorials.
*
[`docs/guides/docker-build.md`](diffhunk://#diff-d72a716938ae527e3acf1f03d8d1175b90657b162d40193501bcdb522ee4b14aR1-R14):
Added a new guide on building Docker images from source, including
Dockerfile locations for various repositories.
*
[`docs/jobs/README.md`](diffhunk://#diff-60d4eafa8c5419228e760194e718b81d1e1d25915292dd52069bfa4b9e216ff4R1-R59):
Added documentation for CI jobs and workflows, including an overview,
job categories, common configurations, job definitions, and best
practices.

---------

Signed-off-by: wuhuizuo <wuhuizuo@126.com>
 (commit: e6dff8f)