startOf() and endOf() don't work as expected when utc() is used

**Describe the bug**
I want to get the last day of the last week of a given month. Similarly, I also want to get the first day of the first week of a given month.
Even though this approach works in local time, it doesn't work when utc() is used.

**Sandbox**: https://codesandbox.io/s/xenodochial-pond-kih9th?file=/src/index.ts

**Expected behavior**
`dayjs('01-01-2022').utc().startOf('month').startOf('week')` should return `2021-12-26`, not `2021-11-29`.
Similarly, `dayjs('01-01-2022').utc().endOf('month').endOf('week')` should return `2022-02-06`, not `2022-01-02`.

**Actual behavior**
(index) | Value
-- | --
start | '2021-12-26T23:00:00.000Z'
end | '2022-02-06T22:59:59.999Z'
startUtc | '2021-11-29T00:00:00.000Z'
endUtc | '2022-01-02T23:59:59.999Z'

Please see the sandbox for more info.
Also - `toISOString()` doesn't work in Firefox or Safari (another bug?!).
So, please open the sandbox in Chrome or replace this method with `format()` or something else.

**Information**
- Day.js Version 1.11.6
- OS: All
- Browser Chrome 107
- Time zone: Central European Standard Time (GMT+1)

Start by reproducing the sandbox case with dayjs().utc().startOf() and endOf(), comparing the UTC and local results in Day.js 1.11.6. Trace the UTC plugin and the week/month boundary behavior; done means the stated start and end dates match in UTC, with the reported browser serialization behavior checked separately.

Written by the indexing model from the issue text.