Reduce number of blobs used in tests to speed up CI (#8194)

`beacon-chain-tests` is now regularly taking 1h+ on CI since Fulu fork was added.

This PR attemtpts to reduce the test time by bringing down the number of blobs generated in tests - instead of generating 0..max_blobs, the generator now generates 0..1 blobs by default, and this can be modified by setting `harness.execution_block_generator.set_min_blob_count(n)`.

Note: The blobs are pre-generated and doesn't require too much CPU to generate however processing a larger number of them on the beacon chain does take a lot of time.

This PR also include a few other small improvements
- Our slowest test (`chain_segment_varying_chunk_size`) runs 3x faster in Fulu just by reusing chain segments
- Avoid re-running fork specific tests on all forks
- Fix a bunch of tests that depends on the harness's existing random blob generation, which is fragile


beacon chain test time on test machine is **~2x** faster:

### `unstable`

```
Summary [ 751.586s] 291 tests run: 291 passed (13 slow), 0 skipped
```

### this branch

```
Summary [ 373.792s] 291 tests run: 291 passed (2 slow), 0 skipped
```

The next set of tests to optimise is the ones that use [`get_chain_segment`](77a9af96de/beacon_node/beacon_chain/tests/block_verification.rs (L45)), as it by default build 320 blocks with supernode - an easy optimisation would be to build these blocks with cgc = 8 for tests that only require fullnodes.


  


Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

Co-Authored-By: Jimmy Chen <jimmy@sigmaprime.io>

beacon_node/execution_layer/src/test_utils/mod.rs

@@ -22,7 +22,7 @@ use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4};
 use std::sync::{Arc, LazyLock};
 use tokio::{runtime, sync::oneshot};
 use tracing::info;
-use types::{ChainSpec, EthSpec, ExecutionBlockHash, Uint256};
+use types::{EthSpec, ExecutionBlockHash, Uint256};
 use warp::{Filter, Rejection, http::StatusCode};
 
 use crate::EngineCapabilities;
@@ -114,7 +114,7 @@ pub struct MockServer<E: EthSpec> {
 }
 
 impl<E: EthSpec> MockServer<E> {
-    pub fn unit_testing(chain_spec: Arc<ChainSpec>) -> Self {
+    pub fn unit_testing() -> Self {
         Self::new(
             &runtime::Handle::current(),
             JwtKey::from_slice(&DEFAULT_JWT_SECRET).unwrap(),
@@ -126,7 +126,6 @@ impl<E: EthSpec> MockServer<E> {
             None, // FIXME(electra): should this be the default?
             None, // FIXME(fulu): should this be the default?
             None, // FIXME(gloas): should this be the default?
-            chain_spec,
             None,
         )
     }
@@ -134,7 +133,6 @@ impl<E: EthSpec> MockServer<E> {
     pub fn new_with_config(
         handle: &runtime::Handle,
         config: MockExecutionConfig,
-        spec: Arc<ChainSpec>,
         kzg: Option<Arc<Kzg>>,
     ) -> Self {
         create_test_tracing_subscriber();
@@ -161,7 +159,6 @@ impl<E: EthSpec> MockServer<E> {
             prague_time,
             osaka_time,
             amsterdam_time,
-            spec,
             kzg,
         );
 
@@ -226,7 +223,6 @@ impl<E: EthSpec> MockServer<E> {
         prague_time: Option<u64>,
         osaka_time: Option<u64>,
         amsterdam_time: Option<u64>,
-        spec: Arc<ChainSpec>,
         kzg: Option<Arc<Kzg>>,
     ) -> Self {
         Self::new_with_config(
@@ -243,7 +239,6 @@ impl<E: EthSpec> MockServer<E> {
                 osaka_time,
                 amsterdam_time,
             },
-            spec,
             kzg,
         )
     }