Configure compression from the store URL

[sduchesneau]

Every store now reads two query parameters on its URL, whatever the scheme:

• compression=zstd|gzip|none overrides the compression given to the constructor and the Compression option. The .zst/.gz suffix of the extension follows it, so NewDBinStore("gs://bucket/path?compression=gzip") writes and reads .dbin.gz. Extensions without a compression suffix (NewSimpleStore, NewStoreFromFileURL) are kept as is.
• compression_config=<level> or <level>/<window MiB> sets the zstd encoder level and window: best, better/32, best/64. It applies to that store only, and is an error on a store that does not compress with zstd.

NewStoreFromFileURL, OpenObject and ReadObject now take the compression from the file name when no Compression option is given (.zst, .gz), so compression_config works there without compression=zstd. They used to read such files as is; ?compression=none keeps that. No caller in our repos relied on it: the firehose-core ones pass Compression("zstd") already.

ObjectURL now puts the store URL query after the object path instead of appending the path to the query.

The settings are per store, so a merger can write merged blocks with best/32 while its one-block store keeps the defaults. An invalid value makes the constructor fail. ResolveCompression is exported and holds these rules.

This bumps klauspost/compress from v1.10.2 to v1.20.1 (Go 1.25), because in v1.10.2 better and best are aliases of default.

Readers need no change for compression_config, since the window comes from the frame header, but they need memory for it. The zstd command line tool refuses windows above 128 MiB by default. Readers do need the same compression as the writer, since it changes file names.

On BNB Chain merged blocks (16-core arm64), savings for every TiB written compressed with the defaults:

config	saved per TiB	encode	decode
default / lib-default (now)	—	879 MB/s	2362 MB/s
better / lib-default	107 GiB (10.5%)	475 MB/s	2466 MB/s
better / 16MB	137 GiB (13.4%)	503 MB/s	1921 MB/s
better / 32MB	142 GiB (13.9%)	490 MB/s	1347 MB/s
better / 128MB	142 GiB (13.9%)	496 MB/s	620 MB/s
best / lib-default	135 GiB (13.2%)	73 MB/s	2512 MB/s
best / 16MB	181 GiB (17.7%)	70 MB/s	1955 MB/s
best / 32MB	229 GiB (22.4%)	66 MB/s	1365 MB/s
best / 64MB	270 GiB (26.4%)	64 MB/s	892 MB/s
best / 128MB	293 GiB (28.6%)	64 MB/s	623 MB/s

[maoueh]

Approving nonethless as this make it easy to experiment for some elements.

[maoueh]

An env var applies bindly to everything, uncertain if it's the default best path. Options available at store creation, ideally via DSN seems like a better way to tweak this on a store per store basis.