You can disable certain IMAP folders in GMail, including the All Mail folder, if you enable the Google Labs "Advanced IMAP Controls". From webmail:
- Go to Settings > Labs and set "Advanced IMAP Controls" to "Enable"
- Once advanced IMAP controls are enabled, you can go to Settings > Labels and uncheck the "Show in IMAP" box next to the folders you want to get rid of (All Mail, Spam, etc.).
- Go back to Evolution and refresh the account, and the folders you unchecked will be gone.
Be warned that you lose functionality if you disable some of those folders, though. If you disable the spam folder, for example, then you can't train GMail's spam filter from Evolution, and disabling the "Trash" folder keeps you from being able to ever delete anything.