Add props for `shrink` and `basis` for `OuiFlexItem`

[BSFishy]

Is your feature request related to a problem? Please describe.

OuiFlexItem only supports the grow property, while shrink and basis are also important and useful properties. There are some cases where they are needed to achieve certain layouts.

Describe the solution you'd like

Add shrink and basis properties for OuiFlexItem. These should be similar to grow but for flex-shrink and flex-basis.

Describe alternatives you've considered

Using custom HTML is an option but is extremely not preferred.

Additional context

This gap was identified in OUI compliance audits:

• https://github.com/opensearch-project/OpenSearch-Dashboards/issues/3966
• https://github.com/opensearch-project/OpenSearch-Dashboards/issues/4122
• https://github.com/opensearch-project/OpenSearch-Dashboards/issues/4162