feat(ui5-side-navigation): initial implementation

[fifoosid]

• Tests are added

Fixes #1871

[ilhan007]

would not it work with standard @ click, instead of firing ui5-_click on mouseup

[ilhan007]

It looks good just couple of things:

• the sub-menu items are expanded with animation in openui5

• check the collapsed mode: the icons are not centred and the borders of the side navigation remains, when collapsed, just the content is squeezed

now:

openui5

• the top separator of the fixed items is different on openui5, it is not 100% width, but smaller,
  here how it should look like

[vladitasev]

I don't mind doing RTL at a later stage, but it would be best to use effectiveDir and set this for the left too

[vladitasev]

Some high level comments:

• Let's keep it to two levels only (like in OpenUI5), but have separate items: side navigation item and side navigation subitem. The subitem won't have the slot and the icon.
• You can try to use the list internally with the TreeListItem, or why not - the whole ui5-tree. The goal is to have the proper design and acc without much overhead. This goes for the special left/right keyboard handling for opening/closing tree nodes.
• When collapsed, and the popup appears, the popup should not be centered around the selected item, but rather should be on the same level:
  
• The user should never have to set width. Width should be set naturally by the items. Furthermore, width is predefined when collapsed, and if the user set width before that, it would be an issue.
• The user should rarely have to set height: if they do - it would be commonly 100% to make it cover the whole page.

[ilhan007]

the default is wrong

[vladitasev]

• I think it makes more sense for Fiori, not main, as it has a very specific UX (dynamic and fixed part - items/subitems), it's not just a standard container.
• When I try to interact with the sample, nothing happens (items do not expand, etc...)
• You should declare a dependency to the tree, and remove the dependency to the list in the .js file

Overall I think this is the right direction (using the tree) as it saves us a lot of code. I'll make a more detailed review tomorrow again, especially around the tree changes.

[ilhan007]

The component is still in "main" package, I think we should move it to "fiori" before we merge it.

[ilhan007]

Another issue: selection is lost

Steps:

1. Select a sub item, f.e. "From My Team"
2. Collapse the Side Nav -> already can be seen that the selection is lost
3. Expand the Side Nav -> no selection is visible

Comments addressed