Reorganize pash_runtime

[angelhof]

No description provided.

[github-actions]

OS:ubuntu-20.04
Wed Apr 19 05:05:36 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS = Debian 10
CPU = Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
Ram = 15752
Hash = 00885b5
Kernel= Linux 4.15.0-197-generic x86_64

benchmark	tests	passed	failed	untested	unresolved	unsupported	not_in_use	other_status
posix	494	375	41	31	6	40	1	0
intro	2	2	0	0	0	0	0	0
interface	39	39	0	0	0	0	0	0
compiler	54	54	0	0	0	0	0	0
aggregator	109	109	0	0	0	0	0	0

[github-actions]

OS:ubuntu-20.04
Wed Apr 19 14:22:38 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS:ubuntu-20.04
Wed Apr 19 14:34:40 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS:ubuntu-20.04
Wed Apr 19 16:16:19 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS:ubuntu-20.04
Wed Apr 19 20:22:10 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS:ubuntu-20.04
Wed Apr 19 20:30:47 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS:ubuntu-20.04
Thu Apr 20 16:31:40 UTC 2023
intro: 2/2 tests passed.
interface: 39/39 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS = Debian 10
CPU = Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
Ram = 15752
Hash = 991020c
Kernel= Linux 4.15.0-197-generic x86_64

benchmark	tests	passed	failed	untested	unresolved	unsupported	not_in_use	other_status
posix	494	374	42	31	6	40	1	0
intro	2	2	0	0	0	0	0	0
interface	39	39	0	0	0	0	0	0
compiler	54	54	0	0	0	0	0	0
aggregator	109	109	0	0	0	0	0	0

[github-actions]

OS:ubuntu-20.04
Fri Apr 21 13:58:38 UTC 2023
intro: 2/2 tests passed.
interface: 40/40 tests passed.
compiler: 54/54 tests passed.
agg: 109/109 tests passed.

[github-actions]

OS = Debian 10
CPU = Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
Ram = 15752
Hash = fe8bb7f
Kernel= Linux 4.15.0-197-generic x86_64

benchmark	tests	passed	failed	untested	unresolved	unsupported	not_in_use	other_status
posix	494	375	41	31	6	40	1	0
intro	2	2	0	0	0	0	0	0
interface	40	40	0	0	0	0	0	0
compiler	54	54	0	0	0	0	0	0
aggregator	109	109	0	0	0	0	0	0

[angelhof]

This PR significantly cleans up the pash runtime. It is now ready to make it an external library. @mgree we can discuss the preferred interface of such a library at some point. What would be the most useful interface. I am thinking something along the lines of:

## Wraps a SCRIPT with a PRE and POST script while making sure to hide this wrapping from SCRIPT
##   by passing it the correct error code and propagating its error code outside while also not resetting `set` state
##   while executing the PRE and POST scripts.
wrap PRE_SCRIPT SCRIPT [POST_SCRIPT]

If we can think of a couple usecases too we can add a cute README and publicize this library as its own repo.