* Flatten spectests directory: Move all spectests to a single directory per network.
Commands ran:
```
cd testing/spectest/
```
Then for each network, I ran the following command twice.
```
find . -type f -name '*_test.go' -exec bash -c '
for file; do
dir=$(dirname "$file")
base=$(basename "$file" _test.go)
new_name="./${dir#./}__${base}_test.go"
git mv "$file" "$new_name"
done
' bash {} +
```
Then updated the packages with a command like
```
sed -i 's/package [a-zA-Z0-9_]\+/package mainnet/g' *.go
```
Updated commit from 5edadd7b to address @Kasey's feedback.
* Fix panic when checking types. String is not compatible with DeepEqual.
* Docs: add commentary on the filename convention
* Add a section about nightly tests to the spectest readme. Ref https://github.com/OffchainLabs/prysm/pull/15312
* Set shard_count to optimal value... one!
* Changelog fragment
* use latest unclog release
* Update spectest build instructions after #9122
---------
Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>
