Properly escape interpolation-like strings in resolved configs

[odelalleau]

Fixes #1112
Fixes #1081

This is a draft PR for several reasons:

1. It needs tests + news fragment
2. It is built on top of Update pre-commit hooks and drop support for Python 3.6 & 3.7 #1109 that needs to be merged first
3. The behavior of to_container() and to_object() needs to be looked at (see Escaped resolver modifying _root_ doesn't work #1120)

Note that this is a breaking change, but it can be argued that the previous behavior was a bug (all tests pass).

[Jasha10]

Looks good to me!

[omry]

I think this needs tests to show what it's actually doing and to ensure it does not break in the future.
Also, worth considering any performance impact.

[odelalleau]

I think this needs tests to show what it's actually doing and to ensure it does not break in the future.

Oh yes (see point 1 above)

Also, worth considering any performance impact.

I need to think about it a bit more, but I don't believe this is an issue. Will keep it in mind though.

[MatteoVoges]

Hey I noticed a breaking change with this. See full description of it here: #1112 (comment)