Update of get_block_with_txs and get_block_with_receipts for peding blocks

[mikiw]

Usage related changes

• Update of get_block_with_txs and get_block_with_receipts for pending blocks

Development related changes

• refactor of business logic related to self.config.blocks_on_demand

Checklist:

• [x] Checked out the contribution guidelines
• [x] Applied formatting - ./scripts/format.sh
• [x] No linter errors - ./scripts/clippy_check.sh
• [x] No unused dependencies - ./scripts/check_unused_deps.sh
• [x] No spelling errors - ./scripts/check_spelling.sh
• [x] Performed code self-review
• [x] Rebased to the latest commit of the target branch (or merged it into my branch)
• [ ] Updated the docs if needed, including the TODO section
• [ ] Linked the issues resolvable by this PR - linking info
• [x] Updated the tests if needed; all passing - execution info

[mikiw]

This PR is addressing @marioiordanov find outs from https://github.com/0xSpaceShard/starknet-devnet-rs/pull/461