[CI] Extract interpreter workflow and split std_spec execution

[straight-shoota]

test_interpreter is failing almost constantly in CI due to running out of memory.

Execution of interpreter-std_spec uses almost 10G memory, but the GHA runners only have around 8G available.

        Command being timed: "bin/crystal i spec/interpreter_std_spec.cr -- --junit_output .junit/interpreter-std_spec.xml"
        User time (seconds): 369.31
        System time (seconds): 4.90
        Percent of CPU this job got: 277%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 2:15.03
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 9926492
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 686100
        Voluntary context switches: 21253
        Involuntary context switches: 6934
        Swaps: 0
        File system inputs: 0
        File system outputs: 6128
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0

Splitting the entire spec suite into separate pieces reduces the total amount of memory. We already have the mechanism with SPEC_SPLIT available. It was previously used for CI on x86.

We should probably try to reduce the interpreters memory usage, but this is a quick workaround to get CI green again.

[Sija]

Several naming suggestions

[Sija]

Naming suggestion to keep consistency with the rest of the workflows.

Suggested change

	name: Interpreter Test
	name: Interpreter CI

[Sija]

Naming consistency-wise:

Suggested change

	test-interpreter_spec:
	test-interpreter-spec:

[straight-shoota]

The spec suite that's being run is called interpreter_spec.

[Sija]

I'd avoid redundant naming (workflow name points at the Interpreter already)

Suggested change

	name: "Test Interpreter"
	name: Test

[Sija]

ditto

Suggested change

	name: Build interpreter
	name: Build

[beta-ziliani]

LGTM