fix(cli): set inputNamePattern to RegExp source instead of string (#2201

)

using RegExp.toString() returns a valid regex string (with / at the beginning and the end of the string), but when this value is reused as RegExp constructor, it tries to covert the string value in to regex, causing the those / to be escaped.
actual: /foo/ /\/foo\// /\/\/foo\/\//
expected: /bar/ /bar/ /bar/

packages/vitest/src/node/stdin.ts

@@ -69,7 +69,7 @@ export function registerConsoleShortcuts(ctx: Vitest) {
       name: 'filter',
       type: 'text',
       message: 'Input test name pattern (RegExp)',
-      initial: String(ctx.config.testNamePattern || ''),
+      initial: ctx.config.testNamePattern?.source || '',
     }])
     await ctx.changeNamePattern(filter, undefined, 'change pattern')
     on()