Replace loading icon (spinner) size md with lg

Minahil Nicholsrequested to merge
change-spinner-size-md into master

What does this MR do and why?

Partly solves #29847 (closed)

*There are currently ~77 instances of size="md" - it will be cleaner/easier to take this in steps.

Screenshots or screen recordings

md lg
image image

How to set up and validate locally

Confirmed/validated manually, example in screenshots.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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