Better solution for indexer's health check and user warning

[Viterbo]

Fixes #697

Description

We are making decisions based on the indexer's health and there are cases where those decisions are made before the indexer is consulted. So we may end up making a bad decision based on the wrong data.

To avoid this problem I added an observable variable to indicate if the indexer was already consulted in such a way that any local query about the health state will always run after the indexer is consulted at least once.

Test scenarios

Reproduce the steps described in the issue #697
You will not get the indexer's health warning sign on Mainnet

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have cleaned up the code in the areas my change touches
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings
• I have removed any unnecessary console messages
• I have included all english text to the translation file and/or created a new issue with the required translations for the currently supported languages
• I have tested for mobile functionality and responsiveness
• I have added appropriate test coverage

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