make OR in journey patterns compile to a valid regular expression
[Testing guide] Use "Fixtures API" instead of "fixture api".
[Testing guide] Using "Fixtures API" consistently

- In guides, "API" is used consistently instead of "api".
- Reason behind replacing "fixtures API" to "Fixtures API" is because
  here we are referring to the concept of "fixtures". In other places in
  the guide "fixture" OR "fixtures" is referred to the single or
  multiple instances of test data.
- This is also followup of https://github.com/rails/docrails/commit/aa9d1332b20305dd860b21a7ada06c5252bebad5#commitcomment-8497376.
Fix grammar on ActiveRecord::AttributeMethods doc.

[ci skip]
FIX: absolute_path may be nil for code added via instance_eval
Merge pull request #17860 from SamSaffron/fix_engine_backtrace

FIX: absolute_path may be nil for code added via instance_eval
Pretty-print request params on exception page
Ensure numericality validations work with mutation

The detection of in-place changes caused a weird unexpected issue with
numericality validations. That validator (out of necessity) works on the
`_before_type_cast` version of the attribute, since on an `:integer`
type column, a non-numeric string would type cast to 0.

However, strings are mutable, and we changed strings to ensure that the
post type cast version of the attribute was a different instance than
the before type cast version (so the mutation detection can work
properly).

Even though strings are the only mutable type for which a numericality
validation makes sense, special casing strings would feel like a strange
change to make here. Instead, we can make the assumption that for all
mutable types, we should work on the post-type-cast version of the
attribute, since all cases which would return 0 for non-numeric strings
are immutable.

Fixes #17852
Merge pull request #17861 from kirs/pp-request-params

Pretty-print request params on exception page
Fix value extracted from negative integers for PostgreSQL.

Fixes: https://github.com/rails/rails/issues/17856.
Merge pull request #17863 from tgxworld/fix_extracated_default_value_for_negative_integers

Fix value extracted from negative integers for PostgreSQL.
tests, use public API to verify default parsing. #17863, #17856
tests, run numeric default tests for every adapter.
Merge pull request #17827 from rkh/rkh-fix-or-pattern

Fix OR in Journey patterns
tests, favor public API over inspecting columns where possible.

This is a follow up to https://github.com/rails/rails/commit/07786c5e75a7b0afdf318063510af6b475e3e04c
and https://github.com/rails/rails/commit/cd2596f55e88fe659592612a793c4f4aa723c9be
Bugfix config.action_view.default_form_builder option
Fix documentation for #default

Just a little syntax error I spotted by accident. Cannot pass hash with curly braces without normal parentheses.
Merge pull request #17869 from 2called-chaos/patch-1

Fix documentation for ActionMailer::Base#default [ci skip]
ugh, forgot to add this test to cdd90f39d796986dabf1678b3277b230dbe18961
Remove unused AV/test/fixtures/blog_public

The fixtures were added to support StaticTests in 401cd97 but
those tests were then removed in d5ad92ce.

If Travis CI is happy with this PR, then you can be sure that
those fixtures are not needed anymore.