Add English names for new PLZA mega evolutions

[jemarq04]

This PR adds entries into pokemon_forms.csv for the new PLZA megas. Additionally, new entries are added into pokemon_form_names.csv for English to match with previous English names for mega evolutions.

To match previous values for order in pokemon_forms.csv, the new mega forms are inserted just after their normal form For example, raichu and raichu-alola are 52 and 53, respectively, and raichu-mega-x and raichu-mega-y are set to 54 and 55. To keep things consistent, all orders greater and equal to 54 are incremented by two (e.g. sandshrew is now 56 and so on). This was done appropriately for all new megas.

Let me know if anything should be modified/added!

[pokeapi-machine-user]

A PokeAPI/api-data refresh has started. In ~45 minutes the staging branch of PokeAPI/api-data will be pushed with the new generated data.

The staging branch will be deployed in our staging environment and the entire API will be ready to review.

A Pull Request (master<-staging) will be also created at PokeAPI/api-data and assigned to the PokeAPI Core team to be reviewed. If approved and merged new data will soon be available worldwide at pokeapi.co.

[pokeapi-machine-user]

The updater script has finished its job and has now opened a Pull Request towards PokeAPI/api-data with the updated data.

The Pull Request can be seen deployed in our staging environment when CircleCI deploy will be finished (check the start time of the last build).