Use new TLS and sel4runtime support

- minimal crt0.S: construct environment in start.c and via the runtime
- update tls init to be compatible with runtime and move initialisation
to after the runtime is initialised
- wait runtime to be initialised in fault handlers

Move component init interfaces to libsel4camkes

These functions are constant and will always be defined by all components and so there is need
for them to be templated. Removing them specifically from the component header also removes the
implication that they should be called by component code when they are intended for internal use
by CAmkES only.

Finally putting these definitions in a library allows them to be used by other library code in
the future, as libraries cannot include per component templates.