Add AVAX as a payment option

[shrnkld]

Scenario:

eth-payment-processor for EXR projects currently allows payment in aBLOCK, aaBLOCK and ETH but not AVAX.

An AVAX address is generated but AVAX doesn't show in the list of accepted tokens. eg:

        'result': {
            'project_id': project_name,
            'api_key': api_key,
            'payment_eth_address': eth_address,
            'payment_avax_address': avax_address,
            'payment_amount_tier1_eth': tier1_expected_amount,
            'payment_amount_tier2_eth': tier2_expected_amount,
            'payment_amount_tier1_ablock': tier1_expected_amount_ablock,
            'payment_amount_tier2_ablock': tier2_expected_amount_ablock,
            'payment_amount_tier1_aablock': tier1_expected_amount_aablock,
            'payment_amount_tier2_aablock': tier2_expected_amount_aablock,
            'expiry_time': payment_expires.strftime("%Y-%m-%d %H:%M:%S EST")
        }

To do:

• [x] add AVAX as an accepted payment currency for exr projects
• [x] add required options for AVAX fee values to the auto-builder

QA:

• [x] snode op can set the AVAX payment values for tier 1
• [x] the relevant project fee is shown in AVAX
• [x] the user is able to pay for a project with AVAX

[shrnkld]

@ConanMishler ok to close this now?

[ConanMishler]

Yeah, I listed this issue as one that would be closed when https://github.com/blocknetdx/eth-payment-processor/pull/35 was merged, but it looks like the auto-closing feature of Github didn't work on this one. Closing now.