update preimage-related docs

[eshaben]

Description

This PR updates the preimage-related docs for the RT2000 breaking changes. Reference: Moonbeam PR description and Substrate PR description

👉 Democracy Pallet Changes:

• note_preimage is moved to pallet-preimages
• note_preimage_imminent has been removed and there is no equivalent
• propose - now accepts a Bounded argument instead of a proposal hash. This can be defined by a proposal hash + length of the proposal, or the call to be executed per se
• Preimages storage item now lives in pallet-preimages

👉A new Preimage Pallet page has been added.

👉 Democracy Precompile Changes:

• The two functions that were not previously supported are now supported so I made appropriate changes there
• Added the associated Events
• Updated the preimage instructions as preimages need to be created now before a proposal can be submitted and it must be done from the new preimages page (Refer to PR description)

👉 How to Submit a Proposal Changes:

• Add all new images
• Submit preimages from the new preimages page

Checklist

• If this requires translations for the moonbeam-docs-cn repo, I have created a ticket for the translations in Jira
• If pages have been moved around, I have created an additional PR in moonbeam-mkdocs to update redirects
• If pages have been moved around, I have run the move-pages.py script to move the pages and update the image paths on the chinese repo
  • After the script has been run, I have created an additional PR in moonbeam-docs-cn
• If images have been added, I have run the compress-images.py script to compress the images.
• If variables (in variables.yml) need to be updated (such as a name change), I have updated the moonbeam-docs-cn repo to use the new variables
• If this page requires a disclaimer, I have added one

Corresponding PRs

moonbeam-foundation/moonbeam-docs-cn#211

After Translation Requirements

• Will need to create PR in moonbeam-docs repo to remove images
• Will need to create PR in moonbeam-docs repo to remove variables
• Will need to create PR in moonbeam-mkdocs repo to add redirects for Chinese site
• No additional PRs are required after the translations are done

Items to be Updated

Remove all of the governance proposals images under the following directory:

• images/tokens/governance/proposals/for-cn/

[albertov19]

Looks good! Left some feedback :)

[eshaben]

Applied all of the feedback and switched around the images so that Xinxin only has to worry about removing images that are no longer needed once translations are done

Had a question about one of the democracy precompile methods, so asked J0 and waiting on an answer before I'll request a review again

[eshaben]

Ok this is good to be reviewed again!

[albertov19]

Great! Ship it 🚢