feat(dateFilter): Add option to display date as am/pm

This adds a new option in order to choose whether to display a date as
AM/PM or am/pm.

Note: This contains a breaking change.  `a` now will display am/pm,
whereas the old behavior is specified by `A` for AM/PM.

This is in support of #8763 .
Just defining things here is not good enough, this needs to work with all the build-in i18n locales. The main issue is that it looks like the CLDR does not distinguish between upper case and lower case of AMPMS