feat!: added MISE_OVERRIDE_CONFIG_FILENAMES config

[jdx]

Before this change, MISE_DEFAULT_CONFIG_FILENAME and MISE_DEFAULT_TOOL_VERSIONS_FILENAME accomplished 2 things where it should only have been doing one.
These commands both ignored "mise.toml"/".tool-versions" (but only that one filename) if set and also changed the default location for commands like mise use to write to.

This made it so you could not set MISE_DEFAULT_CONFIG_FILENAME=.mise.local.toml if you always want to use that file without also ignoring any "mise.toml" files.

This change adds 2 new env vars, MISE_OVERRIDE_CONFIG_FILENAMES and MISE_OVERRIDE_TOOL_VERSIONS_FILENAMES which can be arrays of filenames. If these are set, mise will not load any local filenames (globals are still loaded, use MISE_CONFIG_FILE to change that) and instead mise will use those filenames. For the common pattern of just wanting to ignore .tool-versions you can set MISE_OVERRIDE_TOOL_VERSIONS_FILENAMES=none

As part of this I also did something I wanted to do for a very long time: change MISE_PROFILE to MISE_ENV. mise will still read MISE_PROFILE though so that shouldn't be a breaking change for anyone.

Fixes #1901

BREAKING CHANGE:
This causes mise to start reading mise.toml if MISE_DEFAULT_CONFIG_FILENAME was set previously which it did not before.

This change also changes the behavior slightly for writing new config files. Before it was not consistent across commands like mise settings -l and mise use but now it will use the following order if no file exists and it needs to create one:

• if MISE_DEFAULT_CONFIG_FILENAME is set, create that
• if MISE_OVERRIDE_CONFIG_FILENAMES has anything, use the first.
• if MISE_ENV is set, create "mise.$MISE_ENV.toml"
• else, create "mise.toml"

If you have not been using any of these env vars nothing should change.