Pipeline inputs (#4499)

* initial commit for pipeline inputs from other pipelines

* Add extended example

* add trigger example

* fix kafka header test - headers now lowercase

* Fix cli x-seldon-route and also step tensor map and add step pipeline example

* Update notebook

* Ensure tensorMap works across pipelines by sending pipeline name in tensormap

* Update docs/source/contents/pipelines/index.md

Co-authored-by: Sherif Akoush <sherif.akoush@gmail.com>

* Update docs/source/contents/pipelines/index.md

Co-authored-by: Sherif Akoush <sherif.akoush@gmail.com>

* [SCv2] Improve inference docs re routing and headers (#4481)

* Capitalise Seldon when used as proper noun

* Formatting, capitalisation, etc.

* Add detail to inference docs page

* Formatting and typo fixes

* Use consistent capitalisation of model & pipeline through inference docs page

* Fix typo in inference docs for Kafka topics

* Specify use of inference v2 protocol high up in inference docs

* Add mention of headers to sync inference introduction

* Formatting + minor rewording for clarity

* Use tabs for Compose vs. k8s methods for finding the seldon-mesh endpoint

* Add note on port-forwarding seldon-mesh svc for inference requests

* Add note on service meshes for sending inference requests

* Add section on inference request routing with headers

* Add section on path-based routing for inference endpoints

* Add subsection header for Seldon routing (vs. ingress routing)

* Add section on routing from ingress -> seldon-mesh for inference calls

* Add links to RFCs for host & authority headers

* Update link to RFC for  HTTP/1 Host header

RFC-7230 obsoletes RFC-2616, the previous link.

* Add line describing virtual hosts vs. physical ones

* Use tabs for alternate ways of making inference requests

* Add inference request example with Seldon CLI

* Use consistent capitalisation of v2 for inference protocol

* Add note on Kafka headers for pipelines

* Use ordinal numbering for bullet points

* Update URI for consistency and to avoid confusion

* Move section on making requests above section on routing

* Use interpolation syntax to clarify usage of path-based routing in Seldon mesh

* Add second form of path-based routing for pipelines in Seldon mesh

* Clarify wording re virtual endpoints in SCv2

* Add section for header-based routing examples

This section builds on the examples from the prior section on making inference requests.

* Update basic examples to exclude routing headers

Routing headers are then given in the examples relevant to that section.

* Formatting

* Use group-tabs for example requests with different clients

* Add emphasis to header lines in examples for header-based routing

* Add notes on support for subdomain-based routing

* Add example snippets for subdomain routing

* Add Open Inference schema for iris model for examples

* Move pipeline inference tip lower for better flow

* Fix datatype for iris model inputs

* Bump MLServer version to 1.2.1 (#4503)

* add a notebook test for changing model replicas (#4504)

* Disable autoscaling tracking on agent for models that are fixed (#4501)

* add flag for autoscaling in grpc msg

* autogen files

* extract helper function

* adjust comment

* wire up autoscaling flag in server

* wire up autoscaling in agent client

* set thresholds for scaling in local deployment

* add autoscaling flag to scheduler

* add a toggle for autoscaling service

* revert autoscaling envs set in local deployment

* disable scaling for local deployment

* use a disable toggle instead

* do not disable by default scaling service

* Upgrading docker compose CLI command (#4498)

Not sure if this is necessary but it actually took me some time to figure it out as I was sure that I have `docker compose` already installed. According to the [Docker documentation](https://docs.docker.com/compose/reference/) the spaced version looks like the newer one and maybe the makefile should be updated for that.

* Ensure x-request-id header matches kafka key (#4511)

* Fix possible SIGSEV after producer close in modelgateway (#4515)

* Fix possible SIGSEV after producer close in modelgateway

* Set running after setup

* review comments

* Link how to install docker compose v2 from github releases (#4516)

* link compose github for easier installation

* Update docs/source/contents/getting-started/docker-installation/index.md

Co-authored-by: Alex Rakowski <20504869+agrski@users.noreply.github.com>

Co-authored-by: Alex Rakowski <20504869+agrski@users.noreply.github.com>

* review comments

Co-authored-by: Sherif Akoush <sherif.akoush@gmail.com>
Co-authored-by: Alex Rakowski <20504869+agrski@users.noreply.github.com>
Co-authored-by: Adrian Gonzalez-Martin <agm@seldon.io>
Co-authored-by: Sherif Akoush <sa@seldon.io>
Co-authored-by: Saeid <s.ghafouri@qmul.ac.uk>
Co-authored-by: RafalSkolasinski <r.j.skolasinski@gmail.com>