[lldb][test] Make Linux cpuinfo check more robust (#160675)

We were looking for any mention of the feature name in cpuinfo, which
could have hit anything including features with common prefixes like
sme, sme2, smefa64.

Luckily this was not a problem but I'm changing this to find the
features line and split the features into a list. Then we are only
looking for exact matches.

Here's the information for one core as an example:
```
processor	: 7
BogoMIPS	: 200.00
Features	: fp asimd evtstrm crc32 atomics fphp asimdhp cpuid <...>
CPU implementer	: 0x41
CPU architecture: 8
CPU variant	: 0x0
CPU part	: 0xd0f
CPU revision	: 0
```
(and to avoid any doubt, this is from a CPU simulated in Arm's FVP, it's
not real)

Note that the layout of the label, colon, values is sometimes aligned
but not always. So I trim whitespace a few times to normalise that.

This repeats once for each core so we only need to find one features
line.

0 files changed, 0 insertions, 0 deletions