A new config API is introduced, and ~all of the codebase is adapted to it.
The old API is kept but mainly only for dynamic usage where its extra flexibility is needed.
Using examples, the old config API looked this:
```
>>> config.get("request_expiry", 86400)
604800
>>> config.set_key("request_expiry", 86400)
>>>
```
The new config API instead:
```
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS
604800
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS = 86400
>>>
```
The old API operated on arbitrary string keys, the new one uses
a static ~enum-like list of variables.
With the new API:
- there is a single centralised list of config variables, as opposed to
these being scattered all over
- no more duplication of default values (in the getters)
- there is now some (minimal for now) type-validation/conversion for
the config values
closes https://github.com/spesmilo/electrum/pull/5640
closes https://github.com/spesmilo/electrum/pull/5649
Note: there is yet a third API added here, for certain niche/abstract use-cases,
where we need a reference to the config variable itself.
It should only be used when needed:
```
>>> var = config.cv.WALLET_PAYREQ_EXPIRY_SECONDS
>>> var
<ConfigVarWithConfig key='request_expiry'>
>>> var.get()
604800
>>> var.set(3600)
>>> var.get_default_value()
86400
>>> var.is_set()
True
>>> var.is_modifiable()
True
```
(this somehow escaped attention before, as most objects usually don't have multiple instances,
unless multiple wallets are open at the same time.)
Also, move all signal declarations, class constants and variables to the top of class definitions.
Always use "." as decimal point, and " " as thousands separator.
Previously,
- for decimal point, we were using
- "." in some places (e.g. AmountEdit, most fiat amounts), and
- `locale.localeconv()['decimal_point']` in others.
- for thousands separator, we were using
- "," in some places (most fiat amounts), and
- " " in others (format_satoshis)
I think it is better to be consistent even if whatever we pick differs from the locale.
Using whitespace for thousands separator (vs comma) is probably less confusing for people
whose locale would user "." for ts and "," for dp (as in e.g. German).
The alternative option would be to always use the locale. Even if we decide to do that later,
this refactoring should be useful.
closes https://github.com/spesmilo/electrum/issues/2629
