Resolve "Update presentation for SSO providers on log in page"

What does this MR do?

Changes the styling of social sign in buttons from icons only to buttons in order to match the Google style guidelines. In addition, it removes the 'Didn't receive a confirmation email' and adds a few minor style changes:

• updates SSO provider logos to latest version
• changes 'Register' button style to primary green
• updates provider icons to latest version
• updates Password input help text so it's up to date with the pattern

Screenshots:

before	after

How to setup Omni-Auth Providers for your local GDK:

https://docs.gitlab.com/ee/integration/omniauth.html#supported-providers

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/44943

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #44943 (closed)