bundlespec: fix the generation of bundlespec for `cg.version` If the value is non-default, we display it.

bundlespec: allow the bundle spec to control the bundle version This makes it possible to create bundle using changelog-v3. The `hg debugbundle --spec` output is borked, but this will be fixed in coming changesets.

bundlespec: do not check for `-` in the params portion of the bundlespec Otherwise bundle parameter with `-` in their names result in a crash.

bundlespec: add processing of some parameter value The boolean option needs to be turned into boolean.

bundlespec: extract the parseparams closure It has no value being a closure. We extract it before modifying it further.

bundlespec: test `no` value for the `obsolescence` parameter This is currently broken, but let us test for it first.

bundlespec: test that parameter overwrite the local config This is currently working, but havint it explicitly tested seems useful.

bundlespec: do not overwrite bundlespec value with the config one This is finally making the `obsolete` bundlespec paramater work.

bundlespec: add a `overwrite` parameter to set_param This will open the way for the configuration value to yield in front of the explicit bundle type.

bundlespec: merge the contentopts and params dictionnary They are content using the same keys. Using differents object for access open the gates for confusion in the code using them (this is already the case). So we start fusing their usages to make the parameters more useful. More work will be needed to make them really useful, but the first step is here: not throwing the value away. However this is still not making the previously introduced test useful because currently, the default config value overwrite the one from the bundlespec. We will fix this in the coming changesets.