FR: support environment variables in (favourite) queries

I'd love to see support for using environment variables in favourite queries, or even in all queries.

The use case is that I have several very similar databases where favourite queries all need to take a parameter to indicate what 'variant' of the database I'm currently using, _or_ I have to copy configuration files for each database file and alter one value in each query filter.

Say, the different values are `'foo'` and `'bar'`, and I have to either do:

```ini
favquery1 = '''select ...
from some_table
where parameter='$1'
and other_paramater='$2'
'''
favquery2 = '''select ...
from some_other_table sot inner join a_third_table att on sot.id = att.sot_id
where sot.parameter='$1'
and att.column_name ='$2'
'''
```

and then run `\f favquery1 foo 42` and `\f favquery2 bar 45`, **or** I copy the configuration file multiple times and hardcode the parameter in each.

If, instead, I could use environment variables (syntax suggestion, feel free to come up with better syntax, this is based on bash):

```ini
favquery1 = '''select ...
from some_table
where parameter='${PARAMETER}'
and other_paramater='$1'
'''
favquery2 = '''select ...
from some_other_table sot inner join a_third_table att on sot.id = att.sot_id
where sot.parameter='${PARAMETER}'
and att.column_name ='$1'
'''
```

and then start each `litecli` instance with a different environment variable and use the exact same favourites for each database:

```sh
$ PARAMETER=foo litecli foo_database.sqlite
foo_database.sqlite> \f favquery1 42
```

and

```sh
$ PARAMETER=bar litecli bar_database.sqlite
bar_database.sqlite> \f favquery1 42
```

首先定位 litecli 对收藏查询的处理方式以及 \f 命令的入口点；该 issue 未指定源文件或测试。阅读现有 $1/$2 参数是如何替换的，然后明确环境展开仅适用于收藏查询，还是适用于所有查询。只要约定的语法能够在所示的数据库变体中正常工作，且不破坏现有查询参数，就算完成。

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