Extract CSS from user calendar JS

What does this MR do?

Extracts CSS (fill attributes) from SVGs defined in user calendar JS. This MR refactors the code only, not by changing the color etc.

Offloads bundled JS files up to -66% on /sytses, /gitlab-org, /gitlab-org/gitlab. See !62677 (comment 596203908)

Screenshots (strongly suggested)

No regression confirmed as follows:

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 properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have self-reviewed this MR per code review guidelines.
• I have followed the style guides.