Support custom environment in E2E tests

[pmikolajczyk41]

This PR allows specifying a custom environment for an e2e test with:

#[ink_e2e::test(environment = crate::CustomEnvironment)]
async fn testcase(mut client: Client<C, E>) -> E2EResult<()> {
  ...
}

For an example, see examples/custom-environment.

Message building

Currently, ink_e2e exposes two APIs for message building:

• MessageBuilder that is already generic over environment
• build_message that prepares MessageBuilder for DefaultEnvironment

Generally, build_message is nothing more than MessageBuilder::<DefaultEnvironment, Ref>::from_account_id(account_id). Therefore, I wasn't sure whether we want do anything about it in the context of this PR - I'm open to any suggestion :)

[SkymanOne]

README of the example contracts needs an update; and just few neatpicks from me.
Otherwise, looks good :)

[codecov-commenter]

Codecov Report

Merging #1645 (e289ded) into master (8bc8593) will decrease coverage by 0.03%.
The diff coverage is 69.23%.

@@            Coverage Diff             @@
##           master    #1645      +/-   ##
==========================================
- Coverage   70.72%   70.69%   -0.03%     
==========================================
  Files         206      206              
  Lines        6404     6416      +12     
==========================================
+ Hits         4529     4536       +7     
- Misses       1875     1880       +5     

Impacted Files	Coverage Δ
crates/e2e/macro/src/codegen.rs	0.00% <0.00%> (ø)
crates/e2e/macro/src/config.rs	84.84% <81.81%> (+12.84%)	⬆️
crates/allocator/src/bump.rs	85.95% <0.00%> (-3.13%)	⬇️
crates/ink/ir/src/ast/attr_args.rs	82.60% <0.00%> (-2.18%)	⬇️

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[HCastano]

Only took a quick look, will review again tomorrow

[ganesh1997oli]

Are block_time in this llink which is 6 and timestamp while defining custom environment type Timestamp = <ink::env::DefaultEnvironment as Environment>::Timestamp; same? If so can it be possible to override that value?

[pmikolajczyk41]

@ganesh1233456 these are very different things; block_time = 6 tells that every 6 seconds a new block should be created/finalized; Timestamp is a type used by e.g. pallet timestamp for adding real time info to the block

[HCastano]

Would also be cool to see some UI tests for the E2E macros, but that would be for a future PR

[HCastano]

Almost there!

[HCastano]

I'd also be curious to know what happens if we try and run an E2E test with a custom env on a node that doesn't use one

[pmikolajczyk41]

test added

[HCastano]

Looks good, thanks!

[HCastano]

@SkymanOne since you requested changes we still need another review from you before merging

[SkymanOne]

LGTM!