Add error handling for limits of byte-oriented command line args

[brson]

Some command line arguments have error handling for cases where the arguments are outside of reasonable limits. Several do not. Here are some that I see offhand:

• --cache-grid - Extremely large values hit an intCast assertion. Unreasonably large values are accepted (1000000GB).
• --cache-accounts - small values cause "unreachable" assertions, large values intCast
• --cache-transfers - ditto

[brson]

Note that some of the existing error handling occurs in main.zig, some in cli.zig. It seems reasonable to decide on one place.

[matklad]

Note that some of the existing error handling occurs in main.zig, some in cli.zig. It seems reasonable to decide on one place.

error handling (printing a nice message and exiting the process) should occur in cli.zig.

However, it’s generally a good idea to assert in main (or even at the deepest layer where the value of a particular argument penetrates), that the value is reasonable, as a defense in depth.