Fix custom cache handler importing on windows (#60312)
### Fixing a bug
### What?
Custom cache handler doesn't work on Windows
### Why?
It broke in a recent fix, when adding ESM support - #59863. The problem
is not new - dynamic imports consider an absolute path in Windows as a
protocol:
`ERR! Error [ERR_UNSUPPORTED_ESM_URL_SCHEME]: Only URLs with a scheme
in: file, data are supported by the default ESM loader. On Windows,
absolute paths must be valid file:// URLs. Received protocol 'C:'`
### How?
As a solution, it is necessary to explicitly indicate that it is indeed
an absolute path, for example by adding a / at the beginning, but the
most reliable way is to use pathToFileURL.
Since the logic is repeated in 4 places - I created a common function.
Fixes #58509
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Co-authored-by: JJ Kasper <jj@jjsweb.site>
