Learn - Basic concepts content improvements

The context:

We took the current Massa docs section Architecture -> Introduction, and turned it into a new page which explains basic concepts of Massa blockchain.
The objective of the task is to create additional content, so that readers get a concise, not-too-techy introduction to Massa's main terminology.
Below I wrote suggestion on how to improve each sub-section.

The content structure can be found in this PR #34.

Sub-tasks (per sub-section in docs)

I suggest just linking small PRs for each or each few sections.

**1. Basic concepts → Ledger: -> DONE
To add:

• a few sentences about ledger size limitations, and reasoning why we limit the size of Ledger.

2. Basic concepts → Address: -> DONE
To add:

• Explain functionality of an address, simply, what it can do functionally.
• Define the length of the address object in symbols;
• Explain briefly how are addresses encrypted;
• Explain prefixes in address naming;

3. Basic concepts → Smart Contract:
To add:

• describe versioning of the SC
• update the encryption paragraph as it will change with the testnet 24
• Explain how SCs are different from addresses in terms of functionality (what permissions smart contracts have in terms of ledger read/write access, based on their address)
• Why are they used - mention main use cases.

4. Basic concepts → Autonomous Smart Contract
To add:

• description of the functionality of autonomous smart contracts on Massa
• mention a few practical use-cases that would describe the value ASC brings
  to people familiar with workings of Smart contracts. -> DONE

5. Basic concepts → Storage cost section: -> DONE
To add:

• describe how due to limited ledger space we introduce the storage cost
  concept.
• describe who pays for the storage of smart contracts and how;
• should be linked to the content in 3 sections above (Ledger, Address, SC)

6. Basic concepts → Operations section:
To add:

• Describe what an operation is in a simple way.
• Draw link to 'transactions' as called on other blockchains, so that the first time readers can understand it.
• Mention the length of the Op hash on Massa blockchain. -> DONE

7. Basic concepts → Smart Contract → Execute SC operation:
To add:

• A well described functionality of Execute SC, with a few key examples (~4-5 sentences).
• Mention how Execute SC can be used to perform ledger changes without a need of deploying an SC. This is a unique Massa feature with a lot of usecases that can be mentioned and highlighted as a killer feature. -> DONE
• Connect the content to the table of payload.

8. Basic concepts → Smart Contract → Call SC operation:
To add:

• A well described functionality of Call SC, with a few key examples. (~4-5 sentences)
• Connect the content to the table of payload.

9. Basic concepts → Smart Contract operations -> Tip (:::tip :::)
to add:

• Give simple examples on when to use Execute and when Call SC.
• Redirect to 'tutorials' section if we have any for these Operations

10. Basic concepts → Transaction fee
To add:

• describe the concept of transaction fees at Massa and how the likelihood of Op being added to the block depends on it.
• Introduce gas and gas limit
• briefly introduce how transaction fees relate to gas and gas limit.
• describe how transaction fees serve as rewards to Block creators/stakers.

11. Basic concepts → Block
To add:

• Maximum block size -> DONE
• Explain briefly final and stale blocks and redirect to learn [more](todo redirect to node-architecture.md -> Finalized blocks, stale blocks).