test: integration test storage-types

[peetzweg]

The origin of this PR is the need in the contracts-ui repo to have a contract to test the proper decoding and display of return values of an ink smart contract.

We currently have integration test using the mother contract, however, it's missing some possible types and is relying on inputs for some messages. Testing encoding and sending inputs to an ink! message is should be tested separately.

The original development of this contract happened in a pr for the ink-examples repo before I realised it was a mirror of ink/intergration-tests folder.

Related ink-examples PR: use-ink/ink-examples#15

Related contracts-ui PR: use-ink/contracts-ui#470

cc @statictype

[codecov-commenter]

Codecov Report

Merging #1762 (e12ab8e) into master (fac0225) will decrease coverage by 0.02%.
The diff coverage is n/a.

❗ Current head e12ab8e differs from pull request most recent head 123c4d4. Consider uploading reports for the commit 123c4d4 to get more accurate results

@@            Coverage Diff             @@
##           master    #1762      +/-   ##
==========================================
- Coverage   70.86%   70.84%   -0.02%     
==========================================
  Files         207      207              
  Lines        6655     6655              
==========================================
- Hits         4716     4715       -1     
- Misses       1939     1940       +1     

see 2 files with indirect coverage changes

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[statictype]

Testing encoding and sending inputs to an ink! message is should be tested separately.

the approach of the Mother contract where it returns the input values was ok imo. it allows us to test the encoding of user inputs as well. why do you think it's a problem if we test them together?

[statictype]

we could replace Mother with this. wdyt @agryaznov ?