protoc flag flexibility

[rraymondgh]

Description of changes:
This PR contains three parts

• flake.nix For users / developers that use Nix, setup development environment dependencies

• wasm_package protoc option. This enables a custom version of wasm package to be used

  • there are edge cases where memory leaks are possible. For example:
    

    go-plugin/wasm/host.go

    Line 34 in 6e1c26d

    results, err := malloc.Call(ctx, l)

    
    Never releases this memory. I have a implemented
    

    go-plugin/wasm/plugin.go

    Line 34 in 6e1c26d

    func Malloc(size uint32) uint32 {

    
    and
    

    go-plugin/wasm/plugin.go

    Line 39 in 6e1c26d

    func Free(ptr uint32) {

  to effectively do a TTL on allocations. The use case I have are many short lived requests. This custom implementation is not always applicable. Hence with this flag it adds flexibility to use implementations of these core functions that are more applicable to use case.

• goplugin_known_types This flag enables user to disable go-plugin implementation of known/types. This serves as a way of deprecating these. The use case I have is more assured consistency with https://github.com/piotr-oles/as-proto

For two new flags, both default such that there is no change in behaviour unless user specifies them.

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