CSS-only module. Button colors are reduced to this:

<img width="639" alt="Screenshot 2024-04-14 at 15 36 07"
src="https://github.com/go-gitea/gitea/assets/115237/882d6c02-d1de-44f2-b707-db02a9f5070d">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

I think it's better if the primary actions have primary color instead of
green which fits better into the overall single-color UI design. This PR
currently replaces every green button with primary:

<img width="141" alt="Screenshot 2023-09-16 at 14 07 59"
src="https://github.com/go-gitea/gitea/assets/115237/843c1e50-4fb2-4ec6-84ba-0efb9472dcbe">
<img width="161" alt="Screenshot 2023-09-16 at 14 07 51"
src="https://github.com/go-gitea/gitea/assets/115237/9442195a-a3b2-4a42-b262-8377d6f5c0d1">

Modal actions now use uncolored/primary instead of previous green/red
colors. I also removed the box-shadow on all basic buttons:

<img width="259" alt="Screenshot 2023-09-16 at 14 16 39"
src="https://github.com/go-gitea/gitea/assets/115237/5beea529-127a-44b0-8d4c-afa7b034a490">
<img width="261" alt="Screenshot 2023-09-16 at 14 17 42"
src="https://github.com/go-gitea/gitea/assets/115237/4757f7b2-4d46-49bc-a797-38bb28437b88">

The change currently includes the "Merge PR" button, for which we might
want to make an exception to match the icon color there:

<img width="442" alt="Screenshot 2023-09-16 at 14 33 53"
src="https://github.com/go-gitea/gitea/assets/115237/993ac1a5-c94d-4895-b76c-0d872181a70b">

- Various corrections to button styles, especially secondary
- Remove focus highlight, it's annoying when it stays on button after
press
- Clearly define ghost and link buttons with demos in devtest
- Remove black, grey and tertiary buttons, they should not be used
- Make `arc-green` slightly darker

<img width="1226" alt="image"
src="https://github.com/go-gitea/gitea/assets/115237/8d89786a-01ab-40f8-ae5a-e17f40e35084">
<img width="1249" alt="image"
src="https://github.com/go-gitea/gitea/assets/115237/83651e6d-3c27-46ff-b8bd-ff344d70e949">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

Follow #24097 and #24285

And add a devtest page for modal action button testing.
http://localhost:3000/devtest/fomantic-modal

Now the `modal_actions_confirm.tmpl` could support: green / blue /
yellow positive buttons, the negative button is "secondary".

ps: this PR is only a small improvement, there are still a lot of
buttons not having proper colors. In the future these buttons could be
improved by this approach.

These buttons could also be improved according to the conclusion of
#24285 in the future.



![image](https://user-images.githubusercontent.com/2114189/233847773-a6d6b29b-7b5c-490e-8425-40dfd0ad2529.png)


And add GitHub-like single danger button (context:
https://github.com/go-gitea/gitea/issues/24285#issuecomment-1519100312)


![image](https://user-images.githubusercontent.com/2114189/233891566-055d7611-894d-4d5a-baf5-f6369180bf8d.png)

---------

Co-authored-by: silverwind <me@silverwind.io>

Co-Author: @wxiaoguang 

This PR is to fix
https://github.com/go-gitea/gitea/issues/23318#issuecomment-1506275446 .
The way to fix this in this PR is to use `delete_modal_actions.tmpl`
here both to fix this issue and keep ui consistency (as suggested by
[TODO
here](4299c3b7db/templates/projects/view.tmpl (L161)))

And this PR also refactors `delete_modal_actions.tmpl` and its related
styles, and use the template for more modal actions:

1. Added template attributes:
* locale
* ModalButtonStyle: "yes" (default) or "confirm"
* ModalButtonCancelText
* ModalButtonOkText

2. Rename `delete_modal_actions.tmpl` template to
`modal_actions_confirm.tmpl` because it is not only used for action
modals deletion now.

3. Refactored css related to modals into `web_src/css/modules/modal.css`
and improved the styles.

4. Also use the template for PR deletion modal and remove issue
dependency modal.

5. Some modals should also use the template, but not sure how to open
them, so mark these modal actions by `{{/* TODO: Convert to
base/modal_actions_confirm */}}`

After (Also tested on arc green):

Hovering on the left buttons

<img width="711" alt="Screen Shot 2023-04-23 at 15 17 12"
src="https://user-images.githubusercontent.com/17645053/233825650-76307e65-9255-44bb-80e8-7062f58ead1b.png">

<img width="786" alt="Screen Shot 2023-04-23 at 15 17 21"
src="https://user-images.githubusercontent.com/17645053/233825652-4dc6f7d1-a180-49fb-a468-d60950eaee0d.png">

Test for functionalities:

https://user-images.githubusercontent.com/17645053/233826857-76376fda-022c-42d0-b0f3-339c17ca4e59.mov

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>