Create kernel_rex_version to guard against Rex::Version crashes on local modules

[jheysel-r7]

Summary

PR: #19813 brought up an issue where in some scenarios local modules were sending kernel version strings to Rex::Version.new which were causing crashes.

The PR above resolves the issue by handling errors that occurred when running modules designed for Ubuntu instances on Amazon Linux instances. Amazon Linux has a unique kernel version string, which causes compatibility problems.

We would like to move this functionality into post/linux/kernel as a function (potentially named kernel_rex_version ) so the normalization is centralized and each individual module doesn't have to account for these differences in kernel version strings.

Basic example

The testing done in #19813 should be referenced as it illustrates the issue:

Before the fix the amazon linux version string causes and error:

msf6 exploit(linux/local/vmwgfx_fd_priv_esc) > check
[-] Exploit failed: ArgumentError Malformed version number string 4.14.355-275.572.amzn2.x86_64
[-] MANUAL replacement of trojaned  is required.
[-] Check failed: The state could not be determined.

After the fix the individual module rescues and handles the error:

msf6 exploit(linux/local/vmwgfx_fd_priv_esc) > check
[-] MANUAL replacement of trojaned  is required.
[*] The target is not exploitable. Error determining or processing kernel release (4.14.355-275.572.amzn2.x86_64) into known format: Malformed version number string 4.14.355-275.572.amzn2.x86_64