Fix/subgraph channels

[QYuQianchen]

Fix subgraph of HoprChannel

• Add relation between Account and Channel
• Track stake of an account
• Add Ticket entity

Fixes:

• https://github.com/hoprnet/hopr-devrel/issues/5
• https://github.com/hoprnet/hopr-leaderboard/issues/162

[vercel[bot]]

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[QYuQianchen]

A test version is deployed at https://thegraph.com/legacy-explorer/subgraph/qyuqianchen/hopr-channels?query=Example%20query (for the internal testing HoprChannel contract on polygon)

[0xjjpa]

Awesome! Thanks for taking a look!