- Fix `O(n)` complexity of `append_or_update_attribute`,
  we append objects to an array and re-save project
- Remove the usage of `keys.include?` as it performs `O(n)`
  search, instead use `.has_key?`
- Remove the usage of `.keys.first` as it performs a copy
  of all keys, instead use `.first.first`

Adds frozen string to the following:

* spec/bin/**/*.rb
* spec/config/**/*.rb
* spec/controllers/**/*.rb

xref https://gitlab.com/gitlab-org/gitlab-ce/issues/59758

- rewords examples starting with 'should'
- rewords examples starting with 'it'

Note: I had to manually fixup "onlies" to "only"

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`