Consolidate environment variable docs into one reference - #4989

The environment variables that configure a Temporal Client were spread
across two tables that disagreed with each other and with the code.

docs/references/client-envrionment-configuration.mdx listed 16 variables
and omitted TEMPORAL_PROFILE. docs/cli/setup-cli.mdx listed 10, and
presented TEMPORAL_TLS_CA, TEMPORAL_TLS_CERT, and TEMPORAL_TLS_KEY as
current names when the CLI treats them as legacy compatibility shims
(cliext/client.go). Neither documented the `temporal env` variables or
the remaining legacy TLS names.

Consolidate into a single reference covering all 26 variables, with TOML
key, CLI flag, and Supported by columns. The Temporal CLI is a Temporal
Client, so its variables belong here, marked by scope rather than split
onto a separate page. Ten previously undocumented variables are now
covered: TEMPORAL_PROFILE, TEMPORAL_CLIENT_AUTHORITY, the two
`temporal env` variables, and the six legacy TLS names.

Replace the setup-cli.mdx table with a pointer, keeping its
#environment-variables anchor and absorbing the shell-variable versus
`temporal env` distinction requested in temporalio/cli#776.

Add bin/check-env-config-table.js, which extracts variable names from
every implementation that reads them (sdk-go, sdk-rust core,
sdk-typescript, sdk-java, and the CLI) and fails when the table and the
sources disagree. Descriptions stay hand-written; only the variable and
support data is checked. Runs weekly rather than per PR because it
fetches sources over the network.

Fix the misspelled filename. The URL derives from the frontmatter id, so
it is unchanged and needs no redirect.

The four-column tables scrolled horizontally, hiding the descriptions. Client
settings now use a two-column table with the TOML key and CLI flag folded into
each description. The three variables that not every client reads move to their
own section, one heading each, with TOML key, CLI flag, and a "Read by:" line.

Set toc_max_heading_level: 2 so the per-variable headings give each variable an
anchor without filling the table of contents.

The checker no longer parses a per-client column, so it derives support from the
page structure instead: a table row takes its section's support, and a variable
with its own heading takes its "Read by:" line. An unrecognized section, a
missing "Read by:" line, or a variable that falls under neither rule exits 2
rather than passing quietly, so support cannot silently stop being checked.

The table of contents is built from headings, so putting the variables in it
means each one needs its own heading. Every variable now has an h3 with its
description, TOML key, CLI flag, and "Read by:" line, and the tables are gone.

Group the variables by what they configure rather than by which clients read
them: configuration file, connection, TLS, gRPC metadata, Codec Server, then the
two CLI-only groups. "Client settings" was not a phrase this documentation uses,
and the page is about environment variables either way.

Lead with the intro's precedence order from highest to lowest, and link Temporal
Client to the encyclopedia entry.

Because support now lives on every variable, the checker drops its per-section
rules and reads only "Read by:" lines. A variable reintroduced as a table row
carries no such line, so the checker rejects the row instead of leaving its
support unchecked.

…g-reference