refactor: Reduce memory copying operations in bech32 encoding/decoding

[paplorinc]

Started optimizing the base conversions in TryParseHex, Base58 and IsSpace - this is the next step.

Here I've reduced the memory reallocations and copying operations in bech32 encoding/decoding, resulting in decode being ~22% faster, encode ~32% faster.

Before:

|             ns/byte |              byte/s |    err% |     total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
|                8.67 |      115,400,002.88 |    0.1% |      1.10 | `Bech32Decode`
|               18.76 |       53,300,176.12 |    0.2% |      1.10 | `Bech32Encode`

After:

|             ns/byte |              byte/s |    err% |     total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
|                7.10 |      140,922,648.34 |    0.1% |      1.10 | `Bech32Decode`
|               14.20 |       70,425,968.92 |    0.1% |      1.10 | `Bech32Encode`

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Concept ACK	josibake

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[josibake]

Concept ACK

I cherry-picked your last commit into #30047 to get rid of the hardcoded values inside ExpandHRP. Looking at the rest of your commits here, the rest of the changes look great and the benchmark numbers are a nice improvement. Will review more thoroughly this week!