Refactor Network client layout

[Nana-EC]

Is your feature request related to a problem? Please describe. Currently each call to HederaClient.getClient() creates a new SDK client and doesn't close it's connections Additionally the "clients" that interact with the network are classes that offer static methods to run single operations. There may be improvements that could be made to allow for easy referencing and potential performance gains

Describe the solution you'd like

• Move clients to a single directory each focusing on the entity or transaction type
• Have a single SDK client created at process startup that is utilized in general. If additional are needed due to high TPS e.g. a dedicated client for transfers
• Remove file system logic from TokenClient. Let create() instead take extracted String contents. This should make it easier to test
• Close clients at end of auction

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context

[gregscullard]

Can you explain ?

• Move clients...
• Close clients

I've updated the Hedera client and associated uses to ensure it's only created one (except for the admin apis where injecting a client into the Verticle is problematic unless we only have one instance of the admin vertical - which may be acceptable for low throughput admin requests)

I've also created a new constructor for the HederaClient which accepts all parameters as variables such that we can create one without a dependency on .env.

[gregscullard]

Although, seeing the code uses .env, isn't there value in supplying a test .env file in order to test all is well, rather than override and therefore skip those lines of code during testing ?