fix(inputs.x509_cert): Fix Windows path handling

[srebhan]

• Updated associated README.md.
• Wrote appropriate unit tests.
• Pull request title or commits are in conventional commit format

resolves #10580

This PR fixes the handling of Windows paths by directly creating the URL instead of using a fragile indirection parsing a hand-crafted string.

[powersj]

Thank you for your attention on this one. I am going to leave it to you to merge it, in case you want to wait for PR feedback. Otherwise, feel free to land it before the bug fix next week.

[jjh74]

@jjh74 so do you think we should not support "file://C:/Windows/Temp/test.pem" but "file:///C:/Windows/Temp/test.pem"? If so, please comment on the PR!

If "file://C:/Windows/Temp/test.pem" has worked before then it makes perfect sense to support it.(Probably best if both file://C:/ and file:///C:/ could work).

(AFAIK if you url.Parse file://C:/ with golang(https://go.dev/src/cmd/go/internal/web/url_windows.go) then go interprets file://C:/ as scheme=file, host=C, but I think your patch changes this from url.Parse to &url.URL (no parsing)).

[srebhan]

Both should be supported now on Windows.

[telegraf-tiger]

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DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[aarnaud]

So everything working, I tested these

sources = ["file:///Folder with Space/certs/github.crt"]
sources = ['file://C:\Folder with Space\certs\github.crt']
sources = ["file://C:\\Folder with Space\\certs\\github.crt"]
sources = ["/Folder with Space/certs/github.crt"]
sources = ["file://c:/Folder with Space/certs/github.crt"]
sources = ["file:///c:/Folder with Space/certs/git*.crt"]
sources = ["file://c:/Folder with Space/certs/git*.crt"]
sources = ["file:///Folder with Space/certs/git*.crt"]
sources = ["file:///C:/Folder with Space/certs/github.crt"]