Multiple providers in alpha config (#947)

* Initial commit of multiple provider logic:
1. Created new provider options.
2. Created legacy provider options and conversion options.
3. Added Providers to alpha Options.
4. Started Validation migration of multiple providers
5. Tests.

* fixed lint issues

* additional lint fixes

* Nits and alterations based on CR: manliy splitting large providers validation function and adding comments to provider options

* fixed typo

* removed weird : file

* small CR changes

* Removed GoogleGroups validation due to new allowed-groups (including tests). Added line in CHANGELOG

* Update pkg/apis/options/providers.go

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Update pkg/apis/options/providers.go

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Update pkg/apis/options/providers.go

Co-authored-by: Nick Meves <nick.meves@greenhouse.io>

* Initial commit of multiple provider logic:
1. Created new provider options.
2. Created legacy provider options and conversion options.
3. Added Providers to alpha Options.
4. Started Validation migration of multiple providers
5. Tests.

* fixed lint issues

* additional lint fixes

* Nits and alterations based on CR: manliy splitting large providers validation function and adding comments to provider options

* small CR changes

* auto generates alpha_config.md

* rebase (mainly service alpha options related conflicts)

* removed :

* Nits and alterations based on CR: manliy splitting large providers validation function and adding comments to provider options

* small CR changes

* Removed GoogleGroups validation due to new allowed-groups (including tests). Added line in CHANGELOG

* "cntd. rebase"

* ran make generate again

* last conflicts

* removed duplicate client id validation

* 1. Removed provider prefixes
2. altered optionsWithNilProvider logic
3. altered default provider logic
4. moved change in CHANELOG to 7.0.0

* fixed TestGoogleGroupOptions test

* ran make generate

* moved CHANGLOG line to 7.1.1

* moved changelog comment to 7.1.2 (additional rebase)

Co-authored-by: Yana Segal <yana.segal@nielsen.com>
Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>
Co-authored-by: Nick Meves <nick.meves@greenhouse.io>