⚡ Simplify and speed up thread-data response parsing

[nevans]

One of the examples was incorrectly copied from RFC5256, and a missing SP was added. Note that this PR also makes the parser slightly more strict. We can add workarounds back in, if specific servers send invalid THREAD responses.

Benchmarks:

Calculating -------------------------------------
                              v0.4.5-8-g781b44d       0.4.5
invalid_thread_empty_response          114.984k    100.762k i/s -    343.030k times in 2.983283s 3.404345s
      thread_rfc5256_example1            6.313k      5.228k i/s -     19.183k times in 3.038420s 3.669553s
      thread_rfc5256_example2            6.215k      5.090k i/s -     19.153k times in 3.081493s 3.763122s
      thread_rfc5256_example3          112.226k    113.239k i/s -    349.323k times in 3.112662s 3.084841s
      thread_rfc5256_example4           32.746k     26.211k i/s -     97.246k times in 2.969691s 3.710168s
      thread_rfc5256_example5           60.780k     48.940k i/s -    180.990k times in 2.977799s 3.698196s

Comparison:
   invalid_thread_empty_response
  v0.4.5-8-g781b44d:    114984.1 i/s
              0.4.5:    100762.4 i/s - 1.14x  slower

         thread_rfc5256_example1
  v0.4.5-8-g781b44d:      6313.5 i/s
              0.4.5:      5227.6 i/s - 1.21x  slower

         thread_rfc5256_example2
  v0.4.5-8-g781b44d:      6215.5 i/s
              0.4.5:      5089.7 i/s - 1.22x  slower

         thread_rfc5256_example3
              0.4.5:    113238.6 i/s
  v0.4.5-8-g781b44d:    112226.4 i/s - 1.01x  slower

         thread_rfc5256_example4
  v0.4.5-8-g781b44d:     32746.2 i/s
              0.4.5:     26210.7 i/s - 1.25x  slower

         thread_rfc5256_example5
  v0.4.5-8-g781b44d:     60779.8 i/s
              0.4.5:     48940.1 i/s - 1.24x  slower

Note that the only example that was slower (by a statistically insignificant amount), is merely an empty response. All other examples were significantly faster.