Add message_info and deprecate mock_info (backport #2160)

[mergify]

3 reasons for this:

1. The function is a constructor that does not mock anything
2. We have owned Addr instances and don't want to call .as_str() all the time
3. mock_info is unsafe as it internally uses Addr::unchecked

TODO:

• Implementation
• CHANGELOG entry
• MIGRATING entry for CosmWasm 1 -> 2

  ---

  This is an automatic backport of pull request Add message_info and deprecate mock_info #2160 done by Mergify.

[mergify]

Cherry-pick of 70f8809 has failed:

On branch mergify/bp/release/2.0/pr-2160
Your branch is up to date with 'origin/release/2.0'.

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Changes to be committed:
	new file:   packages/std/src/testing/message_info.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   packages/std/src/testing/mod.rs

Cherry-pick of b4d551e has failed:

On branch mergify/bp/release/2.0/pr-2160
Your branch is ahead of 'origin/release/2.0' by 6 commits.
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You are currently cherry-picking commit b4d551e75.
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Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md

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