Prior to this commit some td in the list renderer were vertically align
on the middle while other are aligned on top. This comes from commit[1]
This commit removes the vertical-align: middle to rely on the inherited
alignment from the `<td>` which is inherited until the `<table>` el
which set the alignment on `top`.
To visually center the icons previously centered by vertical-align,
a new variable: `$o-line-size` is created.
This variable accounts for the total size of a line which is the font
size multiplied by the line height.
In our case this ensure that the icons line height in the list view is
the same as the <td> that are containing text.
[1]: odoo/odoo@53f6053997
task-3557566
closesodoo/odoo#145290
X-original-commit: cce036d03ccd7c12f34ed930b8964e26464732ba
Related: odoo/enterprise#52275
Signed-off-by: Pierre Paridans (app) <app@odoo.com>