[Proposal] Add APIs to configure DCP options

## Background and Motivation

See: https://github.com/dotnet/aspire/pull/7363#discussion_r1938335951

Developers, particularly during testing, occasionally need to modify configuration which is currently only accessible through IConfiguration. Eg, to configure port randomization during testing, dashboard disablement, resource suffixes, etc.

Here are some examples:
- `DcpPublisher:ContainerRuntimeInitializationTimeout`
- `DcpPublisher:RandomizePorts`
- `DcpPublisher:DeleteResourcesOnShutdown`
- `DcpPublisher:ResourceNameSuffix`
- `ASPNETCORE_URLS` (for the AppHost dashboard URL)
- `DOTNET_DASHBOARD_OTLP_ENDPOINT_URL`

## Proposed API

Expose these properties via `DistributedApplicationOptions`, which is passed in to `DistributedApplication.CreateBuilder(DistributedApplicationOptions)` and which is available via the various testing builder creation API overloads on 'DistributedApplicationTestingBuilder`.

## Usage Examples

## Alternative Designs

## Risks