Expose deconstruct api and add tests

[safern]

This is a pick up of the abandoned PR: #14621

The implementation went into corert and coreclr but the APIs where never exposed in the contract nor tests where added.
Fixes: #13746

cc: @ianhays @stephentoub @danmosemsft

[ianhays]

Looks good to me. Thanks for picking this up @safern!

[stephentoub]

Nice. Thanks.

[safern]

@dotnet-bot test Innerloop Windows_NT Debug x86 Build and Test please.

A System.IO.Test failed with the following error:

System.IO.IOException : The process cannot access the file 'C:\\Users\\dotnet-bot\\AppData\\Local\\Temp\\FileInfo_Open_fm_fa_fs_y2jmn1nt.sx1\\FileShareOpen_43' because it is being used by another process.

cc: @JeremyKuhne More details here

[safern]

Thanks for reviewing!

[jcouv]

Looks good.
Will this also be implemented in .NET Framework and Mono? (ping @marek-safar for the latter)
Do we have a process to tag PRs that will need porting?

[safern]

We add the netfx-port-consider to track issues that need porting to full framework, but we do that on the issue itself not on the PR.

The issue is already labeled to port it.

[marek-safar]

@jcouv Mono is tracking the new api and they will be included in upcoming releases

[vanillajonathan]

Is this method documented?