core bug with locale plugin

```js
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('LT')
'12:00 AM'
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('LTS')
'12:00:00 AM'
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('L')
'04/23/2022'
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('LL')
'April 23, 2022'
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('LLL')
'April 23, 2022 12:00 AM'
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('LLLL')
'Saturday, April 23, 2022 12:00 AM'
> dayjs('4/23/22', 'M/DD/YY').locale('en').format('l')
Uncaught TypeError: Cannot read properties of undefined (reading 'replace')
at /Users/user/Projects/web/node_modules/.pnpm/dayjs@1.11.7/node_modules/dayjs/plugin/localizedFormat.js:1:676
at String.replace ()
at /Users/user/Projects/web/node_modules/.pnpm/dayjs@1.11.7/node_modules/dayjs/plugin/localizedFormat.js:1:563
at r.format (/Users/user/Projects/web/node_modules/.pnpm/dayjs@1.11.7/node_modules/dayjs/plugin/localizedFormat.js:1:761)
at e.format (/Users/user/Projects/web/node_modules/.pnpm/dayjs@1.11.7/node_modules/dayjs/plugin/preParsePostFormat.js:1:592)
at u.format (/Users/user/Projects/web/node_modules/.pnpm/dayjs@1.11.7/node_modules/dayjs/plugin/utc.js:1:1655)
> dayjs('4/23/22', 'M/DD/YY').locale('zh').format('l')
'2022/4/23'
> dayjs('4/23/22', 'M/DD/YY').locale('de').format('l')
'23.4.2022'
```

As you can see, there is an uncaught typeerror above for "l", "ll", "lll", and "llll" usage for certain locales, e.g. `en`.

Reproduce the lowercase l, ll, lll, and llll formats with the en locale, then inspect the localizedFormat.js plugin path shown in the stack trace and compare it with the locale definitions used by zh and de. Done means these formats no longer throw for affected locales and retain the expected localized output.

Written by the indexing model from the issue text.