Add API endpoints for asset versioning

In order to enable versioning of the assets in the MLX catalog, we need to add additional API endpoints. This follows closely the approach taken, and API endpoints available for pipeline versions in KFP.

## Existing API Endpoints (i.e. for `components`)

https://ml-exchange.org/apis/v1alpha1/ui/#/ComponentService

/components
GET
POST
/components/{id}
GET
DELETE
/components/{id}/download
GET
/components/{id}/generate_code
GET
/components/{id}/run
POST
/components/{id}/templates
GET
/components/upload
POST
/components/upload_from_url
POST
/components/{id}/upload: ## update existing, currently overrides previous version, will be removed
POST
/components/featured
POST
/components/publish_approved
POST

## New API Endpoints (i.e. `component_versions`)

/component_versions
GET
POST
/component_versions/{version_id}
GET
DELETE
/component_versions/{version_id}/templates
GET
/components/{component_id}/default_version/{version_id}
POST
/components/upload_version
POST

## The properties of the new "version" Swagger object (i.e. `apiComponentVersion`)

- id
- name
- description
- created_at
- tag # semantic tag, like Docker image tags
- code_source_url # GitHub URL including the commit hash corresponding to version in MLX
- ... # remaining asset-specific properties

## Additional properties added to existing Swagger objects (i.e. `apiComponent`)

- default_version
- code_source_url # GitHub URL including the commit hash corresponding to version in MLX