Make TspClient reuseable interface

The new interface is called `ITspClient`.
`ITspClient` can be used for typing and other implementations.
The existing functionality was moved to the `HttpTspClient`.
To not break the existing behavior `TspClient` is still exported as an
alias for the `HttpTspClient`, but is being deprecated.
This way adopters should be notified to migrate to `HttpTspClient`.
This makes the package more flexible as different implementations
can be provided, e.g. a proxy client in a Theia frontend.

Part of eclipse-cdt-cloud/theia-trace-extension#976

Contributed on behalf of STMicroelectronics

tsp-typescript-client/src/index.ts

@@ -12,5 +12,6 @@ export * from './models/trace';
 export * from './models/xy';
 export * from './models/styles';
 export * from './protocol/tsp-client';
+export * from './protocol/http-tsp-client';
 export * from './protocol/rest-client';
 export * from './protocol/tsp-client-response';