windows: Fix various non-portable tests

[darinpp]

Addresses non-portable tests that are failing on Windows.

part of #39079

Release note: None

[cockroach-teamcity]

This change is 

[bdarnell]

Reviewed 5 of 5 files at r1.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @darinpp)

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pkg/base/addr_validation_test.go, line 98 at r1 (raw file):

			addrs{hostAddr + ":26257", hostname + ":12345", hostAddr + ":8080", hostname + ":8080", hostAddr + ":5432", hostname + ":5432"}},

		// Use a non-numeric port number.

Comment that we're using pop3 because it's old enough to be ubiquitous in port mapping files across all platforms.

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pkg/base/store_spec_test.go, line 160 at r1 (raw file):

		if testCase.expected.Path != "" {
			// In case that the testCase has relative path
			testCase.expected.Path, _ = filepath.Abs(testCase.expected.Path)

We should always check errors instead of discarding them.

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pkg/server/status_test.go, line 440 at r1 (raw file):

	t.Run("path separators", func(t *testing.T) {
		// pattern/with/separators on unix
		// pattern\with\separators on windows

I'm not sure if this is what we want. The code tested here is part of debug zip, which won't know to change path separators around based on the platform of the target node. It doesn't matter for now because there doesn't seem to be any current use of this function with a path separator, but it could easily happen. I think it would be better to define the GetFiles interface in terms of URL/posix-style paths and make the GetFiles implementation responsible for translating those paths to those of the local system.