[Hackday] [2.7] Add a deprecation note about TypeTestCase
minor #12968 Deprecations (jzawadzki, dkvk, nicolas-grekas, picur, mrcmorales)

This PR was merged into the 2.7 branch.

Discussion
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Deprecations

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12625, #12605, #12628, #12622, #12642, #12609, #12651, #12604,  #12607, #12667, #12648
| License       | MIT
| Doc PR        | -

Cherry-picking some pending PRs to make them move forward

Commits
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badf8fc [Form] Log deprecation of constants, fixes #12607 #12667
1d58df4 Fix deprecation notice on VirtualFormAwareIterator
e2a19ee Add a deprecation note about VirtualFormAwareIterator
ab4d9b8 Add a deprecation note about CsrfProviderInterface
cb70632 [HttpKernel] fix deprecation notice for Kernel::init()
b5a315d [HttpKernel] Added deprecated error to init()
70012c1 [Hackday] [2.7] Add a deprecation note about TypeTestCase