Audit and update buttons on ProfilesController#show"

What does this MR do?

Updates buttons and avatar layout in ProfilesController#show.

• Use smaller avatar (from 160 → 96).
• Better responsive layout for the Public avatar section.
• Update Choose file button to use GlButton.
• Use sentence case for Public avatar heading.
• Update border color for input group prepended and appended buttons.
• Left align *Update profile settings and Cancel buttons.
  • Increase space above buttons and make them feel more at a page level instead of the last content section.
• Update Cancel button to use GlButton.

Screenshots

Before	After
	CleanShot_2021-05-12_at_08.58.30

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #273315 (closed)