gh-145749: Optimize named exception blocks

[brijkapadia]

Instead of using LOAD_CONST None; STORE_FAST n; DELETE_FAST n for named exception blocks, I changed the bytecode to use PUSH_NULL; STORE_FAST n in an effort to remove the DELETE_FAST instruction.

Not sure if I need a NEWS entry

• Issue: Remove DELETE_FAST bytecode instruction #145749

[Fidget-Spinner]

Deleting a tier 1 (base interpreter) bytecode needs a news entry.

[brijkapadia]

I realized that the reason why some tests do not pass is because STORE_NAME does not currently accept a NULL value. After making that fix, I realized that there are many more errors, all of which would be solved by implementing issue #145854. Thus, I am leaving this PR as a draft until the relevant additions are merged (i.e. PR #146006).