remove tsimp (#10325)

incidental

## Description

Latest `tsimp` is pulling in Rimraf v6 which breaks install under Node 18.

Replace one use of `tsimp` with https://bloomberg.github.io/ts-blank-space/ 

The other import was never used so it simply removes it

### Security Considerations
fewer deps

### Scaling Considerations
none

### Documentation Considerations
none

### Testing Considerations
CI suffices

### Upgrade Considerations
none

multichain-testing/.gitignore

@@ -1,4 +1,3 @@
-.tsimp
 .yarn/*
 !.yarn/patches/*
 # fetched chain info from running starship

multichain-testing/ava.fusdc.config.js

@@ -1,11 +1,6 @@
+import mainConfig from './ava.main.config.js';
+
 export default {
-  extensions: {
-    ts: 'module',
-  },
-  require: ['@endo/init/debug.js'],
-  nodeArguments: ['--import=tsimp/import'],
+  ...mainConfig,
   files: ['test/fast-usdc/**/*.test.ts'],
-  concurrency: 1,
-  serial: true,
-  timeout: '125s',
 };

multichain-testing/ava.main.config.js

@@ -2,8 +2,9 @@ export default {
   extensions: {
     ts: 'module',
   },
-  require: ['@endo/init/debug.js'],
-  nodeArguments: ['--import=tsimp/import'],
+  // Each test imports `@endo/ses-ava/prepare-endo.js` which does its own @endo/init
+  // require: ['@endo/init/debug.js'],
+  nodeArguments: ['--import=ts-blank-space/register'],
   files: ['test/**/*.test.ts', '!test/fast-usdc/**/*.test.ts'],
   concurrency: 1,
   serial: true,

multichain-testing/package.json

@@ -23,23 +23,23 @@
     "@cosmjs/crypto": "^0.32.4",
     "@cosmjs/proto-signing": "^0.32.4",
     "@cosmjs/stargate": "^0.32.4",
-    "@endo/errors": "^1.2.5",
-    "@endo/far": "^1.1.5",
-    "@endo/nat": "^5.0.10",
-    "@endo/ses-ava": "^1.2.5",
+    "@endo/errors": "^1.2.8",
+    "@endo/far": "^1.1.9",
+    "@endo/nat": "^5.0.13",
+    "@endo/ses-ava": "^1.2.8",
     "@types/eslint": "^8",
     "@types/fs-extra": "^11",
     "@types/node": "^20.11.13",
     "@typescript-eslint/eslint-plugin": "^6.20.0",
     "@typescript-eslint/parser": "^6.20.0",
-    "ava": "^6.1.3",
+    "ava": "^6.2.0",
     "eslint": "^8.56.0",
     "eslint-config-prettier": "^9.1.0",
     "execa": "9.1.0",
     "fs-extra": "^11.2.0",
     "patch-package": "^8.0.0",
     "starshipjs": "2.4.1",
-    "tsimp": "^2.0.10",
+    "ts-blank-space": "^0.4.4",
     "tsx": "^4.15.6",
     "typescript": "^5.3.3"
   },