add APIs to execution context for middleware support

[kaibocai]

add APIs to execution context for middleware support

[patriot1burke]

@kaibocai If you add support for the ExecutionContext methods to the Java worker, I can test them out in the Quarkus extension I wrote to integration with azure functions.

[patriot1burke]

Might consider moving these middleware specific methods like setFunctionInstance to a separate interface that extends extends ExecutionContext. ExecutionContext is available to the application developer and these methods might not be something you want exposed to them. See my PR here which shows this:

#10

[kaibocai]

Thank you for your valuable suggestion! We will discuss it with the team.

[kaibocai]

@kaibocai If you add support for the ExecutionContext methods to the Java worker, I can test them out in the Quarkus extension I wrote to integration with azure functions.

Hi @patriot1burke , please use this java worker and this pr core library for local testing.

mvn clean install -Dgpg.skip can install this core library to local maven repo. Thank you.

[kaibocai]

Refer to #10 (comment).
Need to check if function instance has already been set.