Make ActionDispatch::Request::Session#fetch behave like Hash#fetch

Session#fetch was mutating the session when given a default argument
and/or a block. Since Session duck-types as a Hash, it should behave
like one in these cases.
test description uses "disable" when it should be "disabled"
Warn about using `return` inside inline callback blocks [ci skip]

Closes #12981
Merge pull request #13281 from waynn/patch-5

test description uses "disable" when it should be "disabled"
Update CHANGELOG entry for Session#fetch

This reverts the changes to CHANGELOG.md in commit
38f8872aa5fd8f0a1d0895e9eb41f73261acd040.
Merge pull request #13279 from misfo/session-fetch-that-behaves-like-hash-fetch

Make ActionDispatch::Request::Session#fetch behave like Hash#fetch
typos rectified [ci skip]
Merge pull request #13284 from aayushkhandelwal11/typos_corrected

s/everytime/every time/
JSON: speed up date/time encoding

Comparing dates & times with other objects using #== is slow.
Internally, it hits #<=> which calls #to_datetime on objects
that don't respond to it, so we incur the cost of raising an
exception with a possibly-deep backtrace.

Cost of #jsonify on a Time object:

Calculating -------------------------------------
                 old      3644 i/100ms
                 new     12652 i/100ms
-------------------------------------------------
                 old    43373.8 (±3.5%) i/s -     218640 in   5.047017s
                 new   173437.6 (±5.2%) i/s -     872988 in   5.047747s
typos rectified lifecycle => life cycle
Merge pull request #13287 from aayushkhandelwal11/typo_rectified

typos rectified lifecycle => life cycle
Fix typo in action_controller responder.rb
Merge pull request #13288 from dvsuresh/fix_typo

Fix typo in action_controller responder.rb [ci skip]
Changelog improvements [ci skip]
Get rid of hack for freezing time on AR tests

We can now make use of the existent #travel/#travel_to helper methods
added to AS test case and available in all tests.
[ci skip] added after_touch callback documentation

[ci skip] added more explanation for `after_touch` callback
Merge pull request #13032 from kuldeepaggarwal/after_touch_documentation

[ci skip] added after_touch callback documentation [ci skip]
Variants inline syntax documentation [ci skip]

  * Extend method documentation
  * Mention it in actionpack/CHANGELOG
  * Update release notes
Spelling and Grammar checks
Moving the common code of increment and decrement of cache file store into seprate function

Removing the double checking for the value of id

simplifying code for checking conditional code for key

Removing the default values for parameters

removing reduntant code and asiigning value of id in local variable

removing wrongly added line break[ci ckip]

reverting code