Allow configuring TLS Certs from external DWOC

[AObuchow]

Description

#1248 added support for configuring TLS certs in the global DWOC, however this feature cannot be used by an external DWOC.

The reason why setting TLS certs currently only work with the global DWOC is because the certs are used by a HTTP transport object that is shared between all workspaces. Since external DWOC's apply only to the workspace's that references them in their controller.devfile.io/devworkspace-config attribute, we need to be careful to clone (rather than directly modify) the global HTTP transport object when reconciling a workspace. See #1259 (comment)

Additional context

Supporting setting the tlsCertificateConfigmapRef from an external DWOC would allow for eclipse-che/che#22979.