resourceloader: Enable module content version for data modules

resourceloader: Enable module content version for data modules

This greatly simplifies logic required to compute module versions.
It also makes it significantly less error-prone.

Since f37cee996e, we support hashes as versions (instead of timestamps).
This means we can build a hash of the content directly, instead of compiling a
large array with all values that may influence the module content somehow.

Benefits:
* Remove all methods and logic related to querying database and disk for
  timestamps, revision numbers, definition summaries, cache epochs, and more.

* No longer needlessly invalidate cache as a result of no-op changes to
  implementation datails. Due to inclusion of absolute file paths in the
  definition summary, cache was always invalidated when moving wikis to newer
  MediaWiki branches; even if the module observed no actual changes.

* When changes are reverted within a certain period of time, old caches can now
  be re-used. The module would produce the same version hash as before.
  Previously when a change was deployed and then reverted, all web clients (even
  those that never saw the bad version) would have re-fetch modules because the
  version increased.

Updated unit tests to account for the change in version. New default version of
empty test modules is: "mvgTPvXh". For the record, this comes from the base64
encoding of the SHA1 digest of the JSON serialised form of the module content:
> $str = '{"scripts":"","styles":{"css":[]},"messagesBlob":"{}"}';
> echo base64_encode(sha1($str, true));
> FEb3+VuiUm/fOMfod1bjw/te+AQ=

Enabled content versioning for the data modules in MediaWiki core:
* EditToolbarModule
* JqueryMsgModule
* LanguageDataModule
* LanguageNamesModule
* SpecialCharacterDataModule
* UserCSSPrefsModule
* UserDefaultsModule
* UserOptionsModule

The FileModule and base class explicitly disable it for now and keep their
current behaviour of using the definition summary. We may remove it later, but
that requires more performance testing first.

Explicitly disable it in the WikiModule class to avoid breakage when the
default changes.

Ref T98087.

Change-Id: I782df43c50dfcfb7d7592f744e13a3a0430b0dc6