Resolve "Destroying a project causes post_decline_request to be executed"

## What does this MR do?

Ensure we don't send "access request declined" to access requesters when a project is deleted.

## Are there points in the code the reviewer needs to double check?

I've created a service to decouple the notification sending from the AR model.

## Why was this MR needed?

Because there was an issue.

## What are the relevant issue numbers?

Fixes #18755, #18750.

## Does this MR meet the acceptance criteria?

- [x] No CHANGELOG needed.
- [x] Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4744

Move pre_process into render_result

This MR moves `Banzai::Renderer.pre_process` into `Banzai::Renderer.render_result`.

The `pre_process` method was called even when its output would be ignored. See 11a5a4f359ee57029dbfcc9185fc6b47243ea2aa for more details.

See merge request !4830

The method Banzai::Renderer.pre_process would always be called,
regardless of whether the Markdown to render was already cached or not.
In cache the document _was_ cached the output of the pre-processing
pipeline was ignored resulting in it doing nothing but wasting CPU
cycles.

This commit moves Banzai::Renderer.pre_process into
Banzai::Renderer.render_result so that it's _only_ used when needed.

Optimize Banzai::Filter::RelativeLinkFilter

See merge request !4813

    A lot of git operations were being repeated, for example, to build a url
    you would ask if the path was a Tree, which would call a recursive routine
    in Gitlab::Git::Tree#where, then ask if the path was a Blob, which would
    call a recursive routine at Gitlab::Git::Blob#find, making reference to
    the same git objects several times. Now we call Rugged::Tree#path, which
    allows us to determine the type of the path in one pass.

    Some other minor improvement added, like saving commonly used references
    instead of calculating them each time.

Fix builds API response that did not include commit data

## What does this MR do?

This is fix for problem with builds API response not including information about commit this build is created for.

## What are the relevant issue numbers?

Closes #18476 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4827

Show proper image ID on registry page

## What does this MR do?
Display the container registry image ID (from the config blob) instead of the first image layer ID

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?
To show proper image ID on container_registry page.
This only supports manifest V2, since the manifest V1 doesn't expose information about Image ID.

## What are the relevant issue numbers?
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/18159.

## Screenshots (if relevant)
![Screen_Shot_2016-06-21_at_13.16.44](/uploads/db0d3ed8c8b90fafc8dbf1644c2354b0/Screen_Shot_2016-06-21_at_13.16.44.png)

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4821

Allow to fetch LFS from CI

## What does this MR do?

This adds support for fetching LFS object from CI jobs (mostly it's made for supporting GitLab CI).

## What is left?

- [x] Write tests covering a new authorization mechanism

cc @grzesiek @marin

See merge request !4465