[Pal/Linux-SGX] Restrict possible error codes on OCALL returns

[dimakuv]

Description of the changes

As part of OCALL hardening, on OCALL return, we now verify and restrict possibly malicious return values. In most OCALL cases, we check against the set of permissible error codes (taken from corresponding syscall man pages and combined together for multi-syscall OCALLs).

Fixes #634.

How to test this PR?

All tests must pass. Must run several times to be sure.

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This change is 

[dimakuv]

Jenkins, retest this please (first time was successful, running again just to check)

[dimakuv]

Jenkins, retest this please (Jenkins-Debug-18.04 timed out on fcntl14 -- looks like legit timeout; Jenkins-SGX-20.04 failed on test_libos.TC_80_Socket.test_022_poll_closed_fd, known issue fixed by Borys's PR).

Note that all my local 200 runs of fcntl14 succeeded, but the test is indeed pretty slow.

[boryspoplawski]

Jenkins, retest this please (last time was successful, running again just to check)

[boryspoplawski]

Jenkins, retest this please (last time was successful, running again just to check)

[dimakuv]

Jenkins, retest Jenkins-20.04 please (writev07 and fcntl14 timed out...)

[dimakuv]

Jenkins, retest this please (just to be sure)