Clear the circular redirection history of a redirect chain once it is finished

[Amoifr]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Related tickets	fixes #256
License	MIT

What's in this PR?

As suggested in #256, the first commit adds tests: one with a circular redirection over two hops through the real $first callable, which already passes, and two where a new chain reuses the $first instance of a finished chain (ending with a response, then with an exception). Both fail on 2.x with "Circular redirection detected".

The second commit makes the call that starts a chain remove its entry from $circularDetection in a finally, so a reused identifier starts from an empty history and finished chains no longer stay in memory. The line number of the anonymous class in phpstan.neon.dist moves from 221 to 229.

Checklist

• Updated CHANGELOG.md to describe BC breaks / deprecations | new feature | bugfix