feat: Reworking wsl detection logic to avoid false-positives in containers

[rtrevi]

• Removes inspection of /proc/version strings for detecting WSL1 or WSL2. /proc/version is inherited by containers within WSL, causing gcm to wrongly identify these containers as WSL distros: Bug: GCM Misidentifies Docker Containers Running on WSL2 Due to /proc/version #1813

• Inspects /proc/sys/fs/binfmt_misc/WSLInterop and /proc/sys/fs/binfmt_misc/WSLInterop-Late for respectively detecting WSL1 or WSL2. This is consistent across distros and the files aren't inherited into containers.

• Removes inspection of WSL_INTEROP env var for detecting WSL2. Deemed not necessary anymore.

[rtrevi]

First contribution, be gentle :)

[becm]

Sadly #1813 is sort of a collection of curve-balls:

• GetWslVersion was (effectively) fine as-is (albeit I'd support dropping the confusing interop test there)
• detection of "WSL-interop case for the Browser" (the relevant condition) should be a separate check
  • wsl (→ GetWslVersion with uname-only check should be fine)
  • valid mountpoints (sadly GetSystemDriveMountPath has a default fallack → retest required)
  • interop (insert binfmt check here ☺)
  • and only then use Powershell to check SessionId
  • allow falling back to IsDesktopSession (use browser within the WSL or container scope)
• that check must be used consistently at the correct position in OpenDefaultBrowser
• the presence of wslview does not help, as it relies on interop capabilities (and the project is now PPA only).

In the interop-capable case the Browser should to be started by raw

<wslmount>/Windows/System32/cmd.exe /c start <url>

(or an equivalent powershell command) on the host Windows system,
ideally encapsulated in something like WslUtils.openUrl().