refactors AC::Parameters#fetch

AC::Parameters#fetch was refactored in 7171111 to prevent self mutation, but
in doing so it hardcodes logic #convert_hashes_to_parameters is supposed to
encapsulate.

Better leave the delegation, and add a way to avoid mutating self in there.
Add a changelog entry for #13363 [ci skip]
optimizes array conversion in AC::Parameters
Add a changelog entry for #13326 [ci skip]
Fix typo [ci skip]
Fix few typos in the documentation [ci skip]
Enable memcached service on travis for running cache tests.
Merge pull request #13436 from robin850/patch-11

Add missing changelog entries and fix few typos
Merge pull request #13438 from vipulnsward/enable-memache-on-travis

Enable memcached service on travis for running cache tests.
Fix DB Console tests 

The build is broken: https://travis-ci.org/rails/rails/builds/15824530

This commit fixes it.

The problem: Sqlite expects the `database` part to be an absolute path. That prompted this change to be committed to master: https://github.com/rails/rails/commit/fbb79b517f3127ba620fedd01849f9628b78d6ce

This change provides correct behavior. Unfortunately tests were introduced in https://github.com/rails/rails/commit/971d5107cd4cd08c22a85d34546f4ba03ed5c925 that were relying on the incorrect behavior. We can avoid the fix by changing to another database url such as `mysql` or `postgresql`

In addition to fixing the failure, the assertions are changed so that the "expected" value comes before "actual" value.
Use Full path to sqlite database in tests
Merge pull request #13443 from schneems/schneems/fix-master-tests

Fix DB Console tests
Add comments with urls for email previews
Use the same enum definition in the docs and in the comments [ci skip]
fix quoting non-strings

Closes #13444
Merge pull request #13451 from dmathieu/quoting_non_strings

Fix typecasting array of integers
CHANGELOG entry for #13451. [ci skip]
Add missing av/railtie require
Merge pull request #13457 from strzalek/add-missing-av-railtie

Add missing av/railtie require
added test cases for Resolver#connection_url_to_hash