Reduce / eliminate cache misses in interrupt handling

[bjoernQ]

Follow up on #1162 - there are some more insights in the linked issue

Remaining tasks

• [ ] Replace consts this static's if they're referenced in interrupt handling code
• [ ] Put jump tables in RAM
  • Linker magic to place them in RAM on a best effort basis

There is even more to put into RAM to avoid hitting flash. To really see where code accesses flash its best to look at disassembled code

We need to make this opt-in since it will decrease remaining useable RAM which might be a problem for some applications.

Given we don't want to introduce more features this means need #1111 first

[MabezDev]

Now with some configuration options we can opt into placing more of these things into IRAM

[bugadani]

We might want to optimize IRAM code to size. The attribute exists in nightly, so if we want a config to enable nightly-specific features we can do this automagically for all IRAM code.