Audit and update buttons on Projects::IssuesController#new

What does this MR do?

• Move the “Please review the contribution guidelines for this project.” text before the Submit issue and Cancel buttons so that it would be read before submission for screen reader users. This helps make them aware of its presence before submitting the form, in which case it might never be encountered.
• Align Cancel button left.
• Change Submit issue button label to Create issue.
• Update MR approval button order and size.
• Update edit MR and issue button order and variants.

Screenshots

Before	After	Notes
		Text placed before buttons. Buttons left aligned. Submit button label updated to Create.
		Mobile view for above.
		Text placed before buttons. Buttons left aligned. Submit button label updated to Create.
		Mobile view for above.
		Button order changed and Delete irreversible action placed on its own.
		Mobile view for above.
		Buttons reordered, realigned, and use the small size to further next them within the flow and avoid conflict with the footer buttons.
		Mobile view for above.
		Better alignment of buttons to text and each other.
		Updated focus order for new issue
		Updated focus order for editing merge request
		Change button variants, reorder and reposition them.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because _____.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

N/A

Security

N/A

Related to #273313 (closed), #273321 (closed)