It may happen than the routing map is cleared while rendering a qweb
view. For example, if an asset bundle is regenerated, the previous one
is unlinked, which causes a cache clearing.

Previously-generated EndPoint objects aren't found any more in the new
routing map, so `request.endpoint` cannot be used any more after a cache
clearing.

This commit adds hash and comparison magic methods on http.EndPoint so
that EndPoint objects created by a previous routing map generation can
still be used after a cache clearing.

Two tests were added: one to test the comparison and hash methods, and
the other to test them in a real-case rendering.

Commit 80a04f7e fixed this bug too, but introduced another issue
which caused many OPW, so it was quickly reverted by deb23450 along
with its performance improvement 33167b39. This commit replaces
80a04f7e with another way to fix the issue.
A third test has been added in order to avoid reintroducing this other
issue.

By the way, this commit also removes the EndPoint.arguments attribute,
as commit 17f19926 removed all usages of this attribute in Odoo 9.0,
but left this initialization here.

OPW-2834546
OPW-2834549
OPW-2834625

closes odoo/odoo#90745

X-original-commit: 21864908
Signed-off-by: Romain Derie (rde) <rde@odoo.com>