Update chain extension example to show argument passing

[justinfrevert]

This changes the rand-extension Ink! example code to pass along an argument from the contract to the chain extension in the runtime. This PR addresses the first ToDo here, which is a repeat user question. I verified this works in a Substrate node on my machine.

[paritytech-ci]

🦑 📈 ink! Example Contracts ‒ Size Change Report 📉 🦑

These are the results of building the examples/* contracts from this branch with cargo-contract 0.15.0:

	Δ Original Size	Δ Optimized Size	Total Optimized Size
accumulator			6.20 K
adder			7.43 K
contract-terminate			1.50 K
contract-transfer			7.73 K
delegator			10.02 K
dns			21.07 K
erc1155			44.90 K
erc20			10.17 K
erc721			35.20 K
flipper			2.02 K
incrementer			1.92 K
multisig			44.85 K
rand-extension	+0.45 K	+0.41 K	5.08 K
subber			7.44 K
trait-erc20			26.48 K
trait-flipper			1.83 K
trait-incrementer			1.96 K

Link to the run | Last update: Wed Nov 24 07:11:14 CET 2021

[justinfrevert]

The failing CI step seems to be unrelated to this change and prevalent among other current PRs.

[cmichi]

Could you update this comment here and describe the effect of the subject argument?

[codecov-commenter]

Codecov Report

Merging #1029 (d8ae73f) into master (2ee203d) will decrease coverage by 3.74%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1029      +/-   ##
==========================================
- Coverage   78.87%   75.13%   -3.75%     
==========================================
  Files         246      246              
  Lines        9260     9258       -2     
==========================================
- Hits         7304     6956     -348     
- Misses       1956     2302     +346     

Impacted Files	Coverage Δ
crates/lang/ir/src/ir/contract.rs	0.00% <0.00%> (-100.00%)	⬇️
crates/lang/ir/src/ir/ink_test.rs	0.00% <0.00%> (-87.50%)	⬇️
crates/eth_compatibility/src/lib.rs	0.00% <0.00%> (-74.08%)	⬇️
crates/lang/ir/src/ir/trait_def/mod.rs	0.00% <0.00%> (-66.67%)	⬇️
crates/lang/ir/src/ir/blake2.rs	16.66% <0.00%> (-62.50%)	⬇️
crates/lang/ir/src/ir/trait_def/item/trait_item.rs	46.03% <0.00%> (-44.45%)	⬇️
crates/lang/ir/src/ir/trait_def/config.rs	7.69% <0.00%> (-38.47%)	⬇️
crates/lang/ir/src/ir/item_mod.rs	59.73% <0.00%> (-32.22%)	⬇️
crates/lang/ir/src/ir/utils.rs	53.84% <0.00%> (-30.77%)	⬇️
crates/primitives/src/key_ptr.rs	75.00% <0.00%> (-25.00%)	⬇️
... and 18 more

---

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[cmichi]

The failing CI step seems to be unrelated to this change and prevalent among other current PRs.

It's fixed now, it was an issue with one of the GitHub tokens.

[cmichi]

@justinfrevert Could you also merge master into your PR? We think the contract sizes which were posted might be due to your PR being behind master.

[justinfrevert]

Thanks for grabbing it, @HCastano

[cmichi]

Thanks @justinfrevert!

[cmichi]

@justinfrevert Are you up for answering the StackExchange question as well?

[justinfrevert]

@justinfrevert Are you up for answering the StackExchange question as well?

I gave it a shot. Let me know how that looks.

[cmichi]

Great, thx! We should also incorporate your answer into our ink-docs.