Taal: Should we use `@inbounds` + `@boundscheck` to increase standard performance?

I think we should have a discussion about our way of boundschecking in general. There are at least two possible ways:
1. Use more `@boundscheck` blocks and `@inbounds` afterwards to make the assumptions on bounds explicit and the code fast even if the users start Julia with default arguments. While debugging some code, we can start Julia with the flag `--check-bounds=yes` to override `@inbounds`.
2. Do not use `@boundscheck` or `@inbounds` at all. By default, Julia will check bounds on every access. Hence, users need to start Julia with `--check-bounds=no` (or `--check-bounds=0` in @sloede's custom build :wink:) - our status quo.

Personally, I favor the first option.

_Originally posted by @ranocha in https://github.com/trixi-framework/Trixi.jl/pull/203#discussion_r501812901_