fix(vitest): fix false positive file filter match with leading slash

[hi-ogawa]

Description

• closes v.1.5.0 can't pass filters with leading/trailing slashes to CLI #5534
• follow up fix(vitest): correctly filter by parent folder #5408

With the current filter condition, it makes false positive in a following way

dir: /home/hiroshi/code/others/vitest/examples/basic
filter: /basic                             // looks like absolute path but users wish to use to match substring
relativePath = ../../../../../../../basic  // starts with '../..' so filter is true regardless of `testFile`

I'm not sure supporting a filter like /basic has been planned, but I OP's usage makes sense to me.

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