Elastic-charts Usability Enhancements

[markov00]

A list of simple fixes to greatly improve the style of our charts

### Relatively simple tasks
- [ ] https://github.com/elastic/elastic-charts/issues/2121
- [ ] https://github.com/elastic/elastic-charts/issues/2123
- [ ] https://github.com/elastic/elastic-charts/issues/2130
- [ ] https://github.com/elastic/elastic-charts/issues/2125
- [ ] https://github.com/elastic/elastic-charts/issues/2129
- [ ] https://github.com/elastic/elastic-charts/issues/1908
- [ ] https://github.com/elastic/elastic-charts/issues/2126
- [x] https://github.com/elastic/elastic-charts/pull/2004
- [x] https://github.com/elastic/elastic-charts/pull/2005

And few bigger fixes that might be interesting to keep in mind:

### More complex tasks
- [ ] https://github.com/elastic/elastic-charts/issues/2127
- [ ] https://github.com/elastic/elastic-charts/issues/2128
- [ ] https://github.com/elastic/elastic-charts/issues/599