Introduce minimal WireSchema

[tigrannajaryan]

This decouples human-readable Schema that is in JSON
format from WireSchema that is serialized in binary
format for efficiency. WireSchema contains only the
information that is necessary for wire compatibility
checks.

Resolves #24
(Note that we still need struct names for checks).

Here are byte size comparisons between JSON and WIRE
for the Otel/TEF schema with "Metrics" root:

JSON:  2976, zstd:  760
WIRE:   115, zstd:  113

The following components were refactored to use WireSchema
instead of Schema:

• Generated Reader/Writer
• Encoder/Decoders
• gRPC client/server

The Generator continues using JSON Schema as its input, however
it now generates a WireSchema to be used in the generated code.

[tigrannajaryan]

Github action shows benchmark differences, but locally I get parity (as expected, since nothing significant in serialization changed). Local results:

                                │    main     │              binary               │
                                │   sec/op    │   sec/op     vs base              │
SerializeNative/STEF/none-10      3.885m ± 8%   3.724m ± 9%       ~ (p=0.180 n=6)
DeserializeNative/STEF/none-10    1.740m ± 3%   1.709m ± 1%  -1.73% (p=0.002 n=6)
SerializeFromPdata/STEF/none-10   89.18m ± 4%   89.08m ± 5%       ~ (p=0.818 n=6)
DeserializeToPdata/STEF/none-10   22.74m ± 3%   22.73m ± 3%       ~ (p=1.000 n=6)
geomean                           10.82m        10.65m       -1.53%

                                │    main     │              binary               │
                                │  sec/point  │  sec/point   vs base              │
SerializeNative/STEF/none-10      58.10n ± 8%   55.70n ± 9%       ~ (p=0.180 n=6)
DeserializeNative/STEF/none-10    26.02n ± 3%   25.57n ± 1%  -1.73% (p=0.002 n=6)
SerializeFromPdata/STEF/none-10   1.334µ ± 4%   1.333µ ± 5%       ~ (p=0.729 n=6)
DeserializeToPdata/STEF/none-10   340.2n ± 3%   339.9n ± 3%       ~ (p=1.000 n=6)
geomean                           161.8n        159.4n       -1.52%

                                │     main     │               binary               │
                                │     B/op     │     B/op      vs base              │
SerializeNative/STEF/none-10      3.523Mi ± 0%   3.519Mi ± 0%  -0.09% (p=0.041 n=6)
DeserializeNative/STEF/none-10    844.2Ki ± 0%   836.2Ki ± 0%  -0.95% (p=0.002 n=6)
SerializeFromPdata/STEF/none-10   124.7Mi ± 0%   124.7Mi ± 0%       ~ (p=0.818 n=6)
DeserializeToPdata/STEF/none-10   29.82Mi ± 0%   29.81Mi ± 0%  -0.03% (p=0.002 n=6)
geomean                           10.19Mi        10.17Mi       -0.26%

                                │    main     │               binary               │
                                │  allocs/op  │  allocs/op   vs base               │
SerializeNative/STEF/none-10      2.776k ± 0%   2.773k ± 0%        ~ (p=0.058 n=6)
DeserializeNative/STEF/none-10    1.372k ± 0%   1.230k ± 0%  -10.35% (p=0.002 n=6)
SerializeFromPdata/STEF/none-10   256.3k ± 0%   256.4k ± 0%        ~ (p=0.937 n=6)
DeserializeToPdata/STEF/none-10   623.5k ± 0%   623.3k ± 0%   -0.02% (p=0.002 n=6)
geomean                           27.93k        27.17k        -2.72%