refactor: Refactors options merging in chart core

[pan-kot]

Description

Before refactor, we merged the options in two steps:

1. Add RTL-specific overrides for axes
2. Add everything else

After refactor, we still have two steps, but different:

1. Add all options that can be computed before the chart is initialised and chart height is measured
2. Add everything else

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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