GlTokenSelector: Input should reflow with tokens

Previously, the input was in the same flex wrapper as the tokens, meaning it would reflow when tokens were present.

In gitlab-org/gitlab-ui@3d218ce1 this was changed, moving the input out of the same container. As a result when tokens are present the tokens wrap in one column, while the input is to the right, which is unexpected and can cause problems with placeholder text in the input.

This can be observed in the product in the "Linked items" widget on an issue or epic, when adding existing items.

Current	Expected